Systems and methods for vertebral adjustment

ABSTRACT

A system for non-invasively adjusting the curvature of a spine includes a housing having a first end and a second end, a first rod having a first end telescopically disposed within a cavity of the housing along a first longitudinal axis at the first end of the housing and having a first threaded portion extending thereon, and a second end configured to be coupled to a first portion of a spinal system of a subject, a second rod having a first end telescopically disposed within the cavity along a second longitudinal axis at the second end of the housing and having a second threaded portion extending thereon, and a second end configured to be coupled to a second portion of the spinal system of the subject, a driving member rotatably disposed within the cavity and configured to be activated from a location external to the body of the subject.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/270,976, filed Feb. 8, 2019, which is a continuation of U.S.patent application Ser. No. 15/048,928 (now U.S. Pat. No. 10,238,427),filed Feb. 19, 2016, which claims the benefit of priority of U.S.Provisional Application No. 62/118,411, filed Feb. 19, 2015, the entirecontents of which are hereby incorporated by reference into thisdisclosure as if set forth fully herein.

FIELD

The present disclosure relates to systems and methods for distractionwithin the human body. In particular, the present invention relates todistraction devices for the adjustment of sagittal curvature in a spine.

BACKGROUND

Degenerative disc disease affects 65 million Americans. Up to 85% of thepopulation over the age of 50 will suffer from back pain each year.Degenerative disc disease is part of the natural process of aging. Aspeople age, their intervertebral discs lose their flexibility,elasticity, and shock absorbing characteristics. The ligaments thatsurround the disc, known as the annulus fibrosis, become brittle and aremore easily torn. At the same time, the soft gel-like center of thedisc, known as the nucleus pulposus, starts to dry out and shrink. Thecombination of damage to the intervertebral discs, the development ofbone spurs, and a gradual thickening of the ligaments that support thespine can all contribute to degenerative arthritis of the lumbar spine.

When degenerative disc disease becomes painful or symptomatic, it cancause several different symptoms, including back pain, leg pain, andweakness that are due to compression of the nerve roots. These symptomsare caused by the fact that worn out discs are a source of pain becausethey do not function as well as they once did, and as they shrink, thespace available for the nerve roots also shrinks. As the discs betweenthe intervertebral bodies start to wear out, the entire lumbar spinebecomes less flexible. As a result, people complain of back pain andstiffness, especially towards the end of each day.

Depending on its severity and condition, there are many ways to treatdegenerative disc disease patients with fusion being the most commonsurgical option. The estimated number of thoracolumbar fixationprocedures in 2009 was 250,000. Surgery for degenerative disc diseaseoften involves removing the damaged disc(s). In some cases, the bone isthen permanently joined or fused to protect the spinal cord. There aremany different techniques and approaches to a fusion procedure. Some ofthe most common are Anterior Lumbar Interbody Fusion (ALIF), PosteriorLumbar Interbody Fusion (PLIF), Transforaminal Lumbar Interbody Fusion(TLIF), Direct Lateral Interbody Fusion (DLIF), eXtreme LateralInterbody Fusion (XLIF) (lateral), etc. Almost all these techniques nowinvolve some sort of interbody fusion device supplemented with posteriorfixation (i.e., 360 fusion).

Another spinal malady that commonly affects patients is stenosis of thespine. Stenosis is related to degeneration of the spine and typicallypresents itself in later life. Spinal stenosis can occur in a variety ofways in the spine. Most cases of stenosis occur in the lumbar region(i.e., lower back) of the spine although stenosis is also common in thecervical region of the spine. Central stenosis is a choking of thecentral canal that compresses the nerve tissue within the spinal canal.Lateral stenosis occurs due to trapping or compression of nerves afterthey have left the spinal canal. This can be caused by bony spurprotrusions, or bulging or herniated discs.

Non-invasively adjustable devices of the type presented may also be usedin patients having scoliosis, spondylolisthesis, Scheuermann's kyphosis,limb length deformity, limb angle deformity, limb rotational deformity,macrognathia, high tibial osteotomy, or other orthopedic deformities.

SUMMARY

The present disclosure provides various systems for non-invasivelyadjusting the curvature of a spine. One or more embodiments of thosesystems include a housing having a first end and a second end and acavity between the first end and the second end, a first rod having afirst end telescopically disposed within the cavity of the housing alonga first longitudinal axis at the first end of the housing and having afirst threaded portion extending thereon, and a second end configured tobe coupled to a first portion of a spinal system of a subject, a secondrod having a first end telescopically disposed within the cavity of thehousing along a second longitudinal axis at the second end of thehousing and having a second threaded portion extending thereon, and asecond end configured to be coupled to a second portion of the spinalsystem of the subject, a driving member rotatably disposed within thecavity of the housing and configured to be activated from a locationexternal to the body of the subject, a first interface rotationallycoupling a first threaded driver to the driving member, the firstthreaded driver threadingly engaging the first threaded portion of thefirst rod, a second interface rotationally coupling a second threadeddriver to the driving member, the second threaded driver threadinglyengaging the second threaded portion of the second rod, and whereinrotation of the driving member in a first direction causes the firstthreaded driver to move the first end of the first rod into the cavityof the housing along the first longitudinal axis and causes the secondthreaded driver to move the first end of the second rod into the cavityof the housing along the second longitudinal axis.

The present disclosure further provides for a method for adjusting thecurvature of a spine includes providing a non-invasively adjustablesystem including a housing having a first end and a second end and acavity extending between the first end and the second end, a first rodhaving a first end telescopically disposed within the cavity of thehousing along a first longitudinal axis at the first end of the housingand having a first threaded portion extending thereon, and a second endconfigured to be coupled to a first portion of a spinal system of asubject, a second rod having a first end telescopically disposed withinthe cavity of the housing along a second longitudinal axis at the secondend of the housing and having a second threaded portion extendingthereon, and a second end configured to be coupled to a second portionof the spinal system of the subject, a driving member rotatably disposedwithin the cavity of the housing and configured to be activated from alocation external to the body of the subject, a first interfacerotationally coupling a first threaded driver to the driving member, thefirst threaded driver threadingly engaging the first threaded portion ofthe first rod, and a second interface rotationally coupling a secondthreaded driver to the driving member, the second threaded driverthreadingly engaging the second threaded portion of the second rod,wherein rotation of the driving member in a first direction causes thefirst threaded driver to move the first end of the first rod into thecavity of the housing along the first longitudinal axis and causes thesecond threaded driver to move the first end of the second rod into thecavity of the housing along the second longitudinal axis; creating anopening in the skin of a patient as part of a lumbar fusion surgery;coupling the second end of the first rod to a dorsal portion of a firstvertebra of the patient; coupling the second end of the second rod to adorsal portion of a second vertebra of the patient; and closing orcausing to close the opening in the skin of the patient.

The present disclosure still further provides for s system for adjustingthe curvature of a spine includes a housing having a first end and asecond end and a cavity between the first end and the second end, afirst rod having a first end telescopically disposed within the cavityof the housing along a first longitudinal axis at the first end of thehousing and having a first threaded portion extending thereon, and asecond end configured to be coupled to a first portion of a spinalsystem of a subject, a second rod having a first end telescopicallydisposed within the cavity of the housing along a second longitudinalaxis at the second end of the housing and having a second threadedportion extending thereon, and a second end configured to be coupled toa second portion of the spinal system of the subject, a driving memberrotatably disposed within the cavity of the housing and configured to beactivated from a location external to the body of the subject, a firstinterface rotationally coupling a first threaded driver to the drivingmember, the first threaded driver threadingly engaging the firstthreaded portion of the first rod, a second interface rotationallycoupling a second threaded driver to the driving member, the secondthreaded driver threadingly engaging the second threaded portion of thesecond rod, and wherein rotation of the driving member in a firstdirection causes the first threaded driver to move the first end of thefirst rod into the cavity of the housing along the first longitudinalaxis and rotation of the driving member in a second direction, oppositethe first direction, causes the second threaded driver to move the firstend of the second rod into the cavity of the housing along the secondlongitudinal axis.

The present disclosure even further provides for a method for adjustingthe curvature of a spine includes providing a non-invasively adjustablesystem including a housing having a first end and a second end and acavity extending between the first end and the second end, a first rodhaving a first end telescopically disposed within the cavity of thehousing along a first longitudinal axis at the first end of the housingand having a first threaded portion extending thereon, and a second endconfigured to be coupled to a first portion of a spinal system of asubject, a second rod having a first end telescopically disposed withinthe cavity of the housing along a second longitudinal axis at the secondend of the housing and having a second threaded portion extendingthereon, and a second end configured to be coupled to a second portionof the spinal system of the subject, a driving member rotatably disposedwithin the cavity of the housing and configured to be activated from alocation external to the body of the subject, a first interfacerotationally coupling a first threaded driver to the driving member, thefirst threaded driver threadingly engaging the first threaded portion ofthe first rod, and a second interface rotationally coupling a secondthreaded driver to the driving member, the second threaded driverthreadingly engaging the second threaded portion of the second rod,wherein rotation of the driving member in a first direction causes thefirst threaded driver to move the first end of the first rod into thecavity of the housing along the first longitudinal axis and rotation ofthe driving member in a second direction, opposite the first direction,causes the second threaded driver to move the first end of the secondrod into the cavity of the housing along the second longitudinal axis;creating an opening in the skin of a patient as part of a lumbar fusionsurgery; coupling the second end of the first rod to a dorsal portion ofa first vertebra of the patient; coupling the second end of the secondrod to a dorsal portion of a second vertebra of the patient; and closingor causing to close the opening in the skin of the patient.

The present disclosure additionally provides for a system for adjustingthe curvature of a spine including a housing having a first end and asecond end and a cavity extending therein, a first rod having a firstend telescopically disposed within the cavity of the housing along alongitudinal axis at the first end of the housing and having a firstthreaded portion extending thereon, and a second end configured to becoupled to a first vertebra of a spinal system of a subject, a drivingmember rotatably disposed within the cavity of the housing andconfigured to be activated from a location external to the body of thesubject, a second rod extending in a direction generally parallel to thelongitudinal axis, the second rod having a first end coupled to thehousing and a second end configured to be coupled to a second vertebraof the spinal system of the subject, the second vertebra immediatelyadjacent the first vertebra, and wherein the direction from the firstend to the second end of the first rod is generally parallel to thedirection from the first end to the second end of the second rod.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a spinal adjustment implant.

FIG. 2 is a side view of the spinal adjustment implant of FIG. 1 .

FIG. 3A is a cross-sectional view of the spinal adjustment implant ofFIG. 2 , taken along line 3-3.

FIGS. 3B and 3C are enlarged views of the spinal adjustment implant ofFIG. 3A taken from circles 3 B and 3 C, respectively.

FIG. 4 is an embodiment of an external remote controller for use with animplantable device.

FIG. 5 shows the internal components of a handpiece of the externalremote controller of FIG. 4 .

FIGS. 6A-6D show embodiments of spinal adjustment implants, some beingcoupled to lumbar vertebrae.

FIG. 7 is a radiographic image of a spinal fusion segment.

FIG. 8 shows another embodiment of a spinal adjustment implant.

FIG. 9 shows an embodiment of a spinal adjustment implant having apivotable interface.

FIG. 10 shows another embodiment of a spinal adjustment implant.

FIG. 11 is a side view of the spinal adjustment implant of FIG. 10 .

FIG. 12 is a cross-sectional view of the spinal adjustment implant ofFIG. 11 , taken along line 12-12.

FIGS. 13-16 schematically illustrate various embodiments of a drivingelement of a non-invasively adjustable spinal implant.

FIG. 17 shows another embodiment of a spinal adjustment implant.

FIGS. 18-19 are sectional views of the implant of FIG. 17 , taken alongline 18-18.

FIG. 20 illustrates two devices of the embodiment shown in FIG. 19secured to the spinal column in series and having a shared base betweenthem.

FIGS. 21A-21D illustrate an embodiment of a spinal adjustment implantincluding a worm gear and a linkage system that are configured to adjustthe lordotic angle of a vertebra system.

FIG. 22A illustrates the spinal adjustment implant of FIGS. 21A-21Dsecured to a plurality of vertebra of the spinal system.

FIGS. 22B-22C illustrate the implanted spinal adjustment implant of FIG.22A before and after actuation of a drive member that adjusts thelordotic angle of the attached vertebra.

FIGS. 22D-22E illustrate an enlarged view of the implanted spinaladjustment implant of FIG. 22A before and after actuation of a drivemember that adjusts the lordotic angle of the attached vertebra.

FIG. 23A illustrates an embodiment of a spinal adjustment implantincluding one or more gear modules.

FIG. 23B shows the internal components of the spinal adjustment implantof FIG. 23A.

FIG. 23C shows a gear module and other internal components of the spinaladjustment implant of FIGS. 23A and 23B.

FIGS. 24A-D illustrate another embodiment of the spinal adjustmentimplant.

FIG. 25A illustrates an embodiment of a spinal adjustment implantincluding a Torsen differential that is configured to adjust thelordotic angle of a vertebra system. The Torsen differential allows adrive member to drive the two ends of the spinal adjustment implant atthe same or different rate to provide for the same or differentdisplacement rate or angulation rate of change.

FIG. 25B illustrates a top view of the spinal adjustment implant of FIG.25A where the internal gears and drive systems of the spinal adjustmentimplant are visible.

FIG. 25C illustrates a perspective view of the spinal adjustment implantof FIG. 25A with the housing removed.

FIG. 25D illustrates an enlarged view of the Torsen differential of thespinal adjustment implant of the FIG. 25A.

FIG. 25E illustrates a cross-sectional view of the spinal system withthe spinal adjustment implant of FIG. 25A attached and indicating theangles of rotation of the spinal adjustment implant.

FIGS. 26A-26H illustrate a motor or magnet is able to intermittentlylock o unlock a mechanism, as it is adjusted. In some embodiments, theunlocking may temporarily allow for change in angulation, which is thenlocked again, after the change occurs.

FIG. 27 illustrates a hydraulic activated adjustment structure for usein an adjustable spinal implant.

FIG. 28 illustrates a magnetic fluid pump activated adjustment structurefor use in an adjustable spinal implant.

FIG. 29 illustrates a composite fluid coil spring assembly with askeleton structure.

FIG. 30 illustrates a composite fluid coil spring assembly with acompression spring.

FIGS. 31A-31C illustrate different types of springs that may beincorporated, for example into the embodiment of FIG. 30 , to vary theapplication of force as conditions are varied.

FIG. 32 illustrates an implant having a Nitinol spring.

FIG. 33 illustrates an implant having a magnetically operated rotationalratchet.

FIGS. 34A and 34B show various embodiments of harmonic drives that maybe used together with any of the embodiments described herein.

FIG. 35A is an exploded view of a cycloidal drive that may be usedtogether with any of the embodiments described herein.

FIG. 35B is an assembled view of the embodiment illustrated in FIG. 35A.

FIG. 36 shows an embodiment of a roller screw drive that may be usedtogether with any of the embodiments described herein.

FIG. 37 shows a cut-away view of a spur gear that may be used togetherwith any of the embodiments described herein.

FIG. 38 shows a cut-away view of a Torsen-type differential, or wormgear, that may be used together with any of the embodiments describedherein.

FIG. 39 shows a differential screw that may be used together with any ofthe embodiments described herein.

FIGS. 40A-40C illustrate various embodiments of clutches which may beused together with any of the embodiments described herein.

FIG. 41 shows a partial cut-away and partial cross-sectional view of aball screw mechanism that may be used together with any of theembodiments described herein.

FIGS. 42-44 are flow charts, illustrating embodiments of systems oftorque split, differential, and/or gear reduction.

FIGS. 45A-45C show various pivots for coupling rods to pedicle screws.

FIGS. 46A and 46B are detailed views of an embodiment of a pivot havinga sprag clutch.

FIG. 47 shows another embodiment of a pivot coupled to pedicle screwsand vertebrae.

FIG. 48 illustrates an embodiment of a torque-limiting brake isconfigured to lock and unlock a pivot.

DETAILED DESCRIPTION

One or more embodiments of the present invention provide for implantableand adjustable devices that provide fixation and non-invasive adjustmentof the sagittal curvature of the spine. Sagittal imbalance can be anegative aftereffect of some spinal fusion surgeries. Patientsatisfaction with surgery has been correlated with proper restoration ofsagittal balance—patients having a sagittal imbalance have been known toexpress dissatisfaction with their surgery. Spinal fusion surgeriesgenerally involve at least: adding a bone graft material, e.g., aninterbody graft, to at least a portion of the spine (e.g., one of moresegments or vertebrae of the spine); precipitating a physiologicresponse to initiate bone ingrowth (e.g., causing osteogenesis into orfrom or through the bone graft material); and causing a solid bonyfusion to form thereby stopping motion or fusing the portion of thespine being treated. If compression of the interbody graft is notmaintained during/after fusion surgery, instability and/or non-union mayresult. Furthermore, if lumbar lordosis is not maintained during/afterfusion surgery, sagittal balance may be compromised, leading topotential muscle fatigue and pain, among other potential consequences.In some cases, the sagittal balance may be sufficiently compromised tomerit/require revision surgery. Proximal junctional kyphosis(insufficient lumbar lordosis) is a common reason for repeat surgeries.There is a high incidence of insufficient or lower-than-desired lordosisafter lumbar fusion surgery. In fact, it has been estimated that about12% of spines having adjacent segment pathology (sometimes called “flatback syndrome” or “lumbar flat back syndrome”) require repeat,revisionary surgery. Some embodiments of the present invention may beused to non-invasively maintain or change the magnitude of compressionbetween two vertebrae. For example, following a fusion surgery(post-operatively) and/or non-invasively changing the magnitude oflordosis. This may be done to maintain a desired degree of lordosis orto regain a desired degree of lordosis after it has been lost. It mayalso be done to achieve the desired degree of lordosis whenpost-surgical studies (e.g., medical imaging) demonstrate that thedesired degree of lordosis was not achieved during surgery (e.g., fusionsurgery). Some embodiments of the systems and devices disclosed hereincan be used to increase the success of fusion, reduce pseudo-arthrosis(e.g., non-union), and/or increase or preserve sagittal balance. “Finetuning” the magnitude of compression and/or degree of lordosis may allowfor reduced symptoms in portions of the spine, such as those adjacent tothe fusion.

FIGS. 1-3C illustrate a spinal adjustment implant 500 for implantationalong or attachment/coupling to the spinal system of a subject (e.g.,one or more vertebrae). In some cases, the subject may be a patienthaving degenerative disc disease that necessitates fusion of some or allof the lumbar vertebrae through fusion surgery. The spinal adjustmentimplant 500 can be used in place of traditional rods, which are used tomaintain posterior decompression and stabilize during fusion surgery.Some embodiments of the spinal adjustment implant 500 are compatiblewith interbody spacers placed between the vertebrae being treated.

The spinal adjustment implant 500 includes a housing 502 having a firstend 504 and a second end 506. The housing 502 that has a cavity 508generally defining an inner wall 510 and extending between the first end504 of the housing 502 and the second end 506 of the housing 502. Thecavity 508 may have a variable inner diameter along its length (e.g.,the inner diameter of the cavity 508 changes along its length) or mayhave a generally constant inner diameter. Variable inner diametercavities 508 may include one or more ledges, steps, abutments, ramps,chamfered or sloped surfaces, and/or radiused or rounded surfaces, whichmay be used and/or helpful to hold inner components of the spinaladjustment implant 500, as will be discussed in further detail, below.In some embodiments, the inner wall 510 of the housing 502 hascircumferential grooves and/or abutments 512 that axially maintaincertain elements of the assembly (e.g., internal elements). In someembodiments, the abutments 512 include one or more retaining rings orsnap rings.

A driving member 514 may be disposed, placed, or located within thecavity 508 (e.g., rotatably disposed). In some embodiments, the drivingmember 514 includes a non-invasively rotatable element, such asdescribed with respect to FIGS. 20-23 . As illustrated in FIG. 3A, thedriving member 514 may include a cylindrical, radially-poled permanentmagnet 516 secured within a first magnet housing 518 and a second magnethousing 520. The radially-poled permanent magnet may be a cylindrical orpartially cylindrical rare earth magnet and may have two poles, fourpoles, or more. The permanent magnet may be constructed from rare earthmagnet materials, such as Neodymium-Iron-Boron (Nd—Fe—B), which haveexceptionally high coercive strengths. The individual magnets may beenclosed within a stainless steel casing or various layers of nickel,gold or copper plating to protect the magnet material from theenvironment inside the body (or vice versa). In certain embodiments,other magnetic materials may be used, including, but not necessarilylimited to, SmCo₅ (Samarium Cobalt) or AlNiCo (Aluminum Nickel Cobalt).In other embodiments, Iron Platinum (Fe—Pt) magnets may be used. Ironplatinum magnets achieve a high level of magnetism without the risk ofcorrosion, and may possibly preclude the need to encapsulate. In yetother embodiments, the permanent magnet may be replaced by magneticallyresponsive materials such as Vanadium Permendur (also known as Hiperco).

The first and second magnet housings 518, 520 may, together, provide aninternal cavity to hold the cylindrical, radially-poled, permanentmagnet 516. In some embodiments, the internal cavity created by thehousings 518, 520 is longer than the length of the cylindrical,radially-poled, permanent magnet 516, thus leaving at least somelongitudinal space 522. In other embodiments, the internal cavity issubstantially the same side as the cylindrical, radially-poled,permanent magnet 516. The first and second magnet housings 518, 520 maybe welded or bonded to each other, as well as to the cylindrical,radially-poled, permanent magnet 516. These two design features(i.e., 1. an internal cavity that is longer than the magnet, and 2. afirst and second housing that are fixed to each other and/or the magnet)may together serve to limit or eliminate compressive and/or tensilestresses on the cylindrical, radially-poled permanent magnet 516. Thefirst and second magnet housings 518, 520 may be made from robustmaterials (e.g., titanium alloys) in order to provide strength at acomparatively small wall thickness. Of course, as will be readilyunderstood, any of a number of other materials may be used.

In the embodiment of FIGS. 1-3A, the driving member 514 (e.g., drivesystem, actuator, motor, driver) is positioned longitudinally betweentwo abutments 512 by two radial bearings 524, which facilitate freerotation of the driving member 514 about a driving member axis 526. Insome embodiments, the abutments 512 incorporate a cornered surface, suchas, for example, ledges, steps, corners, etc. In other embodiments, theabutments 512 incorporate a flat or curved surface, including, forexample, ramps, chamfered or sloped surfaces, and/or radiused or roundedsurfaces. In some embodiments, one or more of the radial bearings 524are replaced by thrust bearings and/or angular bushings. In someembodiments, the bearings comprise stainless steel. In some embodiments,the bearings comprise 400 series stainless steel. In some embodiments,the bearings comprise electro-polished 316 stainless steel, PEEK, or acombination of these. Forming the bearings out of PEEK and/or platingthe bearings may increase efficiency by as much as about 50% or up toabout 80% or more. Depending on the locations of the abutments 512, thebearings may advantageously serve to minimize axial stresses on one ormore portions of the drive train of the spinal adjustment implant 500,including, but not limited to one or more of the radially-poledpermanent magnet 516, the housings 518, 520, the lead screw(s) (to bediscussed in additional detail, below), the connection(s) between themagnet and the lead screw (i.e., the pin-based connection).Additionally, the bearings generally allow the system to minimizefrictional resistance, thereby reducing the amount of torque required tooperate the system, or increasing the possible resultant amount oftorque/force that can be generated.

Referring to FIGS. 3A-3C, a first threaded driver 528 (e.g., a leadscrew, a screw, a threaded rod, a rotating driver) is connected to thefirst magnet housing 518 and, therefore, also, the cylindrical,radially-poled permanent magnet 516. In some embodiments the firstthreaded driver 528 is connected to the first magnet housing 518 using aconnection that allows some axial movement, play, or slop between thetwo (e.g., leaving the two not axially over-constrained). For example,the first threaded driver, 528 may have a hole 532 (e.g., aperture,port, opening) extending substantially horizontally through the firstend 530 of the first threaded driver, 528. In much the same way, thefirst magnet housing 518 may have one or more holes 534 (e.g., aperture,port, opening) extending substantially horizontally therethrough, forexample, through an annular projection 538. The hole 532 in the firstend 530 may be configured so that it may align with the one or moreholes 534 in the annular projection 538. A holder, such as a pin 536 orother fixer, can extend though the one or more holes 534 in the annularprojection 538 and the hole 532 in the first end 530 of the firstthreaded driver, 528, thus creating an interface 540 which rotationallycouples the driving member 514 to the first threaded driver 528. In someembodiments, the annular projection 538 and the first end 530 areotherwise rotationally coupled.

In much the same way, a second threaded driver 542 (e.g., a lead screw,a screw, a threaded rod, a rotating driver) is connected to the secondmagnet housing 520 and, therefore, also, the cylindrical, radially-poledpermanent magnet 516. In some embodiments the second threaded driver 542is connected to the second magnet housing 520 using a connection thatallows some axial movement, play, or slop between the two (e.g., leavingthe two not axially over-constrained). For example, the second threadeddriver 542 may have a hole 546 (e.g., aperture, port, opening) extendingsubstantially horizontally through the first end 544 of the secondthreaded driver 542. Similarly, the second magnet housing 520 may haveone or more holes 548 (e.g., aperture, port, opening) extendingsubstantially horizontally therethrough, for example, through an annularprojection 550. The hole 546 in the second end 544 may be configured sothat it may align with the one or more holes 548 in the annularprojection 550. A holder, such as a pin 552 or other fixer, can extendthough the one or more holes 548 in the annular projection 550 and thehole 546 in the first end 544 of the second threaded driver 542, thuscreating an interface 554 which rotationally couples the driving member514 to the second threaded driver 542. In some embodiments, the annularprojection 550 and the first end 544 are otherwise rotationally coupled.

In some embodiments, the driving member 514 is directly, mechanicallycoupled to one or both of the first threaded driver 528 and the secondthreaded driver 542, such as was described above with respect to the cupand pin structure of the pin and annular flange. However, in otherembodiments, the driving member 514 is indirectly coupled to one or bothof the first threaded driver 528 and the second threaded driver 542,such as through a gearing system or another type of step down. Gearingsystems may advantageously decrease the torque required to generate agiven force. In embodiments in which the driving member 514 is directly,mechanically coupled to one or both of the first threaded driver 528 andthe second threaded driver 542, rotation of the driving member 514 infirst rotational direction 556 causes the rotation of both the firstthreaded driver 528 and the rotation of the second threaded driver 542in the same direction, i.e., the first rotational direction 556. In thesame way, rotation of the driving member 514 in second rotationaldirection 559 causes the rotation of both the first threaded driver 528and the rotation of the second threaded driver 542 in the samedirection, i.e., the second rotational direction 559. Though the firstand second threaded drivers 528, 542 are illustrated in this embodimentas being screws with male threads, in other embodiments, they may alsobe hollow rods having internal (female) threads along at least a portionof their length (e.g., all or less than all).

With continued reference to FIGS. 1-3A, the first threaded driver 528and the second threaded driver 542 may have opposite thread handedness.The first threaded driver 528 may have a right-handed male thread 560. Afirst rod 558 (e.g., extendible or retractable portion) has a first end562 telescopically disposed within the cavity 508 of the housing 502,and a second end 564 configured to be coupled to a portion a patient,such as, for example, a portion of the skeletal system. In someembodiments, as illustrated in FIGS. 1-3A, the second end 564 of thefirst rod 558 is configured to be coupled to a first portion of theskeletal system, such as, but not limited to a first portion of thespinal system (e.g., a first vertebra), via a first extension member566. The first portion of the spinal system may be a first vertebra.Alternatively, the second end 564 of the first rod 558 may be coupled toa first vertebra directly, via one or more of: a pedicle screw; hook;wire; or other attachment system(s). As shown in FIGS. 1-3A, the firstextension member 566 may comprise a rod portion 568 and a base portion570. The base portion 570 may be secured to the second end 564 of thefirst rod 558 using a set screw 572 (e.g., by tightening the set screw572) or other fastener/fastening device. A flat portion 573 may belocated on a portion of the first rod 558, in order to provide a surfacefor interfacing with an end of the set screw 572, for example, toimprove resistance to loosening of the set screw 572 with respect to thefirst rod 558. The rod portion 568 of the first extension member 566 maybe coupled to a first vertebra directly, via one or more of: a pediclescrew; hook; wire; or other attachment system(s). As may be seen in FIG.6A, the first extension member 566 a may extend generally transverselywith respect to the housing 502 and/or first rod 558 a.

Referring again to FIGS. 1-3A, the first end 562 of the first rod 558may include a cavity 574 having a first threaded portion 576incorporating a right-handed female thread 580 configured to mate withthe right-handed male thread 560 of the first threaded driver 528. Insome embodiments, one of which is shown in FIG. 3C, the cavity 574comprises a nut 578 bonded or otherwise secured therein. Theright-handed male thread 560 of the first threaded driver 528 and theright-handed female thread 580 of the first rod 558 threadingly engageeach other such that rotation of the driving member 514 in the firstrotational direction 556 causes the first threaded driver 528 to turn inthe same first rotational direction 556, thereby causing the first rod558 to move into the cavity 508 of the housing 502 along a firstlongitudinal axis 582 (FIG. 1 ), in a first longitudinal direction 584.

The second threaded driver 542 may comprise a left-handed male thread586. A second rod 588 (e.g., extendible or retractable portion) has afirst end 590 telescopically disposed within the cavity 508 of thehousing 502, and a second end 592 configured to be coupled a portion apatient, such as, for example, a portion of the skeletal system. In someembodiments, as illustrated in FIGS. 1-3A, the second end 592 of thesecond rod 588 is configured to be coupled to a second portion of thespinal system via a second extension member 594. The second portion ofthe spinal system may be a second vertebra. Alternatively, the secondend 592 of the second rod 588 may be coupled to a second vertebradirectly, via one or more of: a pedicle screw; hook; wire; or otherattachment system. As shown in FIGS. 1-3A, the second extension member594 may comprise a rod portion 596 and a base portion 598. The baseportion 598 may be secured to the second end 592 of the second rod 588using a set screw 599 (e.g., by tightening the set screw 599). The rodportion 596 of the second extension member 594 may be coupled to asecond vertebra directly, via one of more of: a pedicle screw; hook;wire; or other attachment system. As may be seen in FIG. 6A, the secondextension member 594 a may extend in a generally transversely withrespect to the housing 502 a and/or second rod 588 a. Referring again toFIGS. 1-3A, the first end 590 of the second rod 588 may include a cavity597 having a first threaded portion 595 incorporating a left-handedfemale thread 593. In some embodiments, one of which is shown in FIG.3B, the cavity 597 comprises a nut 591 bonded or otherwise securedtherein. The left-handed male thread 586 of the second threaded driver542 and the left-handed female thread 593 of the second rod 588threadingly engage each other such that rotation of the driving member514 in the first rotational direction 556 causes the second threadeddriver 542 to turn in the same first rotational direction 556, therebycausing the second rod 588 to move into the cavity 508 of the housing502 along a second longitudinal axis 589 (FIG. 1 ), in a secondlongitudinal direction 587.

The driving member 514 in combination with the first threaded driver 528and the second threaded driver 542 may therefore comprise a turnbuckle,such that their rotation in the first rotational direction 556 causesboth the first rod 558 and second rod 588 to move into the cavity 508 ofthe housing 502, thus causing the longitudinal distance L between pointsA and B to decrease. This motion is capable of generating a force on thespine at the points of attachment and increasing the compressiveforce(s) between vertebrae. Rotation of the driving member 514, firstthreaded driver 528 and second threaded driver 542 in a secondrotational direction 559, opposite the first rotational direction 556,causes both the first rod 558 and second rod 588 to move out of thecavity 508 of the housing 502, thus causing the longitudinal distance Lbetween points A and B to increase. This motion is capable of generatinga force on the spine at the points of attachment and decreasing thecompressive force(s) between vertebrae.

In some embodiments, the first threaded driver 528 and the secondthreaded driver 542 may have the same thread handedness. Both the firstthreaded driver 528 and the second threaded driver 542 may have aright-handed male thread. Alternatively, both the first threaded driver528 and the second threaded driver 542 may have a left-handed malethread. As described above, when the first threaded driver 528 and thesecond threaded driver 542 have opposite thread handedness, rotation ofthe two in the same direction (such as by rotation of the cylindrical,radially-poled, permanent magnet) will cause the first threaded driver528 and the second threaded driver 542 to move in oppositedirections—depending on the right or left thread handedness, rotation ina first direction will cause both threaded drivers to retract into thehousing while rotation in the second, opposite direction will cause boththreaded drivers to distract from or extend out of the housing. Bycontrast, when both the first threaded driver 528 and the secondthreaded driver 542 have an identical thread handedness (i.e., bothright or both left) rotation of the cylindrical, radially-poled,permanent magnet will cause the first and second threaded drivers tomove in opposite directions with respect to the housing—depending on theright or left thread handedness, rotation in a first direction willcause the first threaded driver 528 to retract into the housing whilecausing the second threaded driver 542 to distract from or extend out ofthe housing (assuming the other or the right or left thread handedness,rotation in the opposite, second direction will cause the first threadeddriver 528 to distract from or extend out of the housing while causingthe second threaded driver 542 to retract into the housing). As will bediscussed in more detail below, a third extension member 581 having arod portion 579 and a base portion 577 may be reversibly or fixedlycoupled to the housing 502. For example, the base portion 577 may besecured to the housing 502 by tightening a set screw 575.

The driving member 514 in combination with the first threaded driver 528and the second threaded driver 542 may therefore selectively generate aforce between two vertebrae (e.g., the vertebrae to which the firstextension member 566 and the third extension member 581 are attached)while decreasing the force between the two adjacent vertebrae (e.g., thevertebrae to which the third extension member 581 and the secondextension member 594 are attached). In effect, such a system can move atop (or bottom) vertebra closer to a middle vertebra, while moving abottom (or top) vertebra away from the middle vertebra. Rather thancausing motion, this system (as well as any of the other systemsdisclosed herein) may generate force without causing motion. Though, itis likely that at least some motion will accompany the generation offorce, whether it be a distraction force or a compressive force.

To seal the interior contents of the cavity 508 of the housing 502,seals 585, for example, dynamic seals, (shown in FIGS. 3B-3C) may bedisposed between each of the first and second rods 558, 588 and thehousing 502. The dynamic seals 585 may comprise o-rings, and may becontained within a circumferential groove on either the exterior of therods 558, 588 or the interior of the housing 502. Of course, many othersealing systems are contemplated, such as but not limited to expandablehydrogel-based systems, bellows or flexible sheaths covering the overlapof the housing and the rod(s), etc.

In some embodiments, one or more of the housing and the rods has ananti-rotation member or a key to prevent rotation of the housing withrespect to the rods (and therefore the third extension member 581 withrespect to one or both of the first and second extension members 566,594). For example, in some embodiments, the housing 502 has a protrusion(not shown) configured to engage longitudinal grooves 583 on the rods558, 588. The protrusion maintains rotational alignment of each of therods 558, 588 with respect to the housing 502 and allows the rods 558,588 to move (e.g., extend and extend, retract and retract, extend andretract, or retract and extend) longitudinally with respect to eachother while preventing significant rotation with respect to one another.In some embodiments, the anti-rotation member or element preventssubstantially all rotational movement of the housing with respect to therods (or vice versa). In other embodiments, the anti-rotation member orelement prevents all rotational movement of the housing with respect tothe rods (or vice versa). In still other embodiments, the anti-rotationmember or element prevents less than about 10 degrees, less than about 8degrees, less than about 6 degrees less than about 4 degrees, or lessthan about 2 degrees of rotational motion of the housing with respect tothe rods (or vice versa). Thus, when the spinal adjustment implant 500is secured to a fusion patient's spine, instrumented portions of thespine can be held static to one another, and substantial movement mayonly occur when the spinal adjustment implant 500 is adjusted. In someembodiments, substantial fixation of the rotational alignment betweeneach of the rods 558, 588 and the housing 502 is achieved by a memberattached at the end of the housing. In other embodiments, substantialfixation of the rotational alignment between each of the rods 558, 588and the housing 502 is achieved by the rods having non-circularcross-sections (e.g., ovoid, hexagonal, square, a geometric shape, etc.)which are “keyed” to a similarly non-circular cavity (e.g., a matingcavity) within the housing.

The second ends 564, 592 of the first and second rods 558, 588 and therod portions 568, 596 of the first and second extension members 566, 594may be sized similar to standard spinal rods. In this way, the secondends 564, 592 of the first and second rods 558, 588 and the rod portions568, 596 of the first and second extension members 566, 594 may be fixedto the skeletal system or coupled to fixation devices using standard,off-the-shelf orthopedic hardware, such as pedicle screws or otherwise.In some embodiments, the second ends 564, 592 of the first and secondrods 558, 588 and the rod portions 568, 596 of the first and secondextension members 566, 594 have transverse dimensions, or diameters, inthe range of about 3-7 mm, in the range of about 3.5-6.35 mm, greaterthan about 3.5 mm, greater than about 4.5 mm, or greater than about 5.5mm. The housing 502 may be coupled to a third portion of the spinalsystem, for example, a third vertebra via a third extension member 581having a rod portion 579 and a base portion 577. The base portion 577may be secured to the housing 502 by tightening a set screw 575. Ofcourse, it will be understood that, while adjustability can beadvantageous in some applications, in other applications, any one ormore of the first, second, and third extension member may be permanentlyfixed to the housing and/or the rods (for example, by welding,monolithic formation, or otherwise).

A system incorporating the spinal adjustment implant 500 according tovarious embodiments of the present invention, may use an External RemoteController (ERC). FIG. 4 illustrates an example of an External RemoteController (ERC) 180 which may be used to non-invasively control thespinal adjustment implant 500 by means of a magnetic coupling of torque.ERC 180 comprises a magnetic handpiece 178, a control box 176(containing a processor) which may be integrated with the handpiece 178and a power supply 174 such as a battery or external plug for connectionto a standard power outlet. The control box 176 includes a control panel182 having one or more controls (buttons, switches or tactile, motion,audio or light sensors) and a display 184. The display 184 may bevisual, auditory, tactile, the like, or some combination of theaforementioned features, or any other display/UI described in thisdisclosure. The control box 176 may further contain a transceiver forcommunication with a transceiver in the implant and/or other externaldevices.

FIG. 5 illustrates an internal assembly 478 of the magnetic handpiece178 configured for applying a moving magnetic field to allow fornon-invasive adjustment of the spinal adjustment implant 500 by turningthe cylindrical, radially-poled permanent magnet 516 within the spinaladjustment implant 500. The cylindrical, radially-poled permanent magnet516 of the spinal adjustment implant 500 includes a north pole 406 and asouth pole 408. A motor 480 with a gear box 482 outputs to a motor gear484. The motor gear 484 engages and turns a central (idler) gear 486,which has the appropriate number of teeth to turn first and secondmagnet gears 488, 490 at identical rotational speeds. First and secondmagnets 492, 494 turn in unison with the first and second magnet gears488, 490, respectively. Each magnet 492, 494 is held within a respectivemagnet cup 496 (shown partially). An exemplary rotational speed is 60RPM or less. This speed range may be desired in order to limit theamount of current density included in the body tissue and fluids, tomeet international guidelines or standards. As seen in FIG. 5 , thesouth pole 498 of the first magnet 492 is oriented the same as the northpole 404 of the second magnet 494, and likewise, the first magnet 492has its north pole 400 oriented the same and the south pole 402 of thesecond magnet 494. As these two magnets 492, 494 turn synchronouslytogether, they apply a complementary and additive moving magnetic fieldto the cylindrical, radially-poled permanent magnet 516. Magnets havingmultiple north poles (e.g., two or more) and multiple south poles (e.g.,two or more) are also contemplated in each of the devices.Alternatively, a single magnet (e.g., a magnet with a larger diameter)may be used in place of the two magnets. As the two magnets 492, 494turn in a first rotational direction 410 (e.g., counter-clockwise), themagnetic coupling causes the cylindrical, radially-poled permanentmagnet 516 to turn in a second, opposite rotational direction 412 (i.e.,clockwise). The rotational direction of the motor 480 is controlled bybuttons 414, 416. One or more circuit boards 418 contain controlcircuitry for both sensing rotation of the magnets 492, 494 andcontrolling the rotation of the magnets 492, 494. Alternatively, one ormore electromagnets may be used in place of or in conjunction with themagnets 492, 494.

Two spinal adjustment implants 500 a, 500 b coupled bilaterally to threelumbar vertebrae are shown in FIG. 6A. The first spinal adjustmentimplant 500 and second spinal adjustment implant 500 b may be secured tothe spinal system 600 as is described below. The first rod 558 as of thefirst spinal adjustment implant 500 a is secured to the L5 lumbarvertebra 602 by a pedicle screw 604 a, while the first rod 558 b of thesecond spinal adjustment implant 500 b is secured to the L5 lumbarvertebra 602 by a pedicle screw 604 b. The second rod 588 a of the firstspinal adjustment implant 500 a is secured to the L3 lumbar vertebra 608by a pedicle screw 604 c, while the second rod 588 b of the secondspinal adjustment implant 500 b is secured to the L3 lumbar vertebra 608by a pedicle screw 604 d. The first rods 558 a, 558 b and second rods588 a, 588 b may be coupled to the pedicle screws 604 a, 604 b, 604 c,604 d via first and second extension members 566 a, 566 b, 594 a, 594 b.The housings 502 a, 502 b may be secured by pedicle screws 606 a, 606 b,via third extension members 581 a, 581 b, to the L4 lumbar vertebra 610.Such securement of the housings 502 a, 502 to an intermediary vertebra(L4, 610) between the two vertebrae to be adjusted (L5 and L3, 602, 608)helps assure that the implants 500 a, 500 b maintain set locations onthe spinal system 600 and can serve as reference points to theadjustment of the first rods 558 a, 558 b and second rods 588 a, 588 b.Adjusting the spinal adjustment implants 500 a, 500 b by rotatingdriving member 514 in the first direction 556 (FIG. 3A) increasescompression on and between the L5 lumbar vertebra 602 and L3 lumbarvertebra 608. Increasing compression on implants such as those shown inFIG. 6 may advantageously increase lordosis in the sagittal plane. Thespinal adjustment implants 500 a, 500 b may be secured to the dorsal(posterior) side of the vertebrae 602, 608, 610. In such an implantationconfiguration, when the implants 500 a, 500 b decrease in length(causing compression), the dorsal sides of the vertebrae 602, 608, 610(the locations of pedicle screw insertion) may be brought closertogether than the anterior (ventral) sides of the vertebrae 602, 608,610 (opposite the side of pedicle screw insertion). That differentialdisplacement increases the angle of lordosis.

FIG. 6B illustrates an embodiment of an adjustment implant. The implantincludes a housing 650. In some embodiments, the housing is formedmonolithically. However, in other embodiments, the housing is formedfrom two halves joined at a joint (e.g., a threaded or welded joint)651. Using a housing formed from two halves may advantageously ease themanufacturing and assembly process, particularly for parts, such as thethrust bearings, which are held by features of the inner wall of thehousing (such as abutments). The implant also includes a first rod 660and a second rod 661.

The first rod 660 has a proximal end that is at least partiallycontained within the housing and has a first rod hollow or cavity 662.The proximal portion of the first rod 660 contained within the housingmay have a slot, groove, or other linear feature 666 on at least part ofits surface. As will be explained below, the slot 666 may serve as aportion of an anti-rotation system. The first rod 660 also has a distalend that extends away from the housing and is used to attach the deviceto the skeletal system of a patient/subject. In some embodiments, therod 660 is straight prior to implantation. In other embodiments, the rod660 is curved prior to implantation. In yet other embodiments, the rod660 is bendable prior to or during surgery, for example, by animplanting surgeon, so that the rod may best conform to the individualpatient into which it is being implanted. The rod may be fixed directlyto the patient's skeletal system, for example, using standard pediclescrews. Alternatively, the rod 660 may be attached to the patient'sskeletal system using a keyhole extender system that holds the rod 660some distance away from the skeletal system. The keyhole extender systemmay include a ring 664 off of which a shaft or bar extends. The ring 664may be slid up and down the rod 660, thereby improving adjustability.Once the desired position of the ring 664 is identified, it may bereversibly fixed to the rod 660 using a set screw 670.

The proximal end of the first rod 660 has an outer diameter that is justsmaller than an inner diameter of the housing 650. In that way, a sealmay be formed by using conventional methods, such as o-rings. FIG. 6Bshows an annular groove containing an o-ring on an outer surface of theproximal end of the first rod 660. However, it should be understood thata groove for containing an o-ring may be included on the inner surfaceof the housing.

The housing 650 may be hollow across its entire length. However, whilethe housing 650 may be hollow, the inner diameter may change across itslength. For example, the housing 650 may include one or more corners,steps or abutments to hold one or more internal features of the device,such as portion(s) of the drive train, for example one or more bearing(e.g., thrust bearings and/or radial bearings). As shown in FIG. 6B, thehousing 650 includes a step or abutment that holds a radial bearing,which, in turn, holds axially a spindle of the rotating magnet 652(e.g., a spindle of a housing holding the magnet 652, or a spindle thatextends through and is axially fixed with respect to the magnet 652).The housing 650 is also shown as having a set screw, key, or protrusion646 that mates with the slot to prevent rotation of the rod 660 withrespect to the housing 650. In some embodiments, the rod 660 may have aplurality of slots 666 while the housing has a single protrusion 646. Inthat way, the rotational orientation of the rod 660 with respect to thehousing 650 may be changed by merely withdrawing the protrusion 646,rotating the rod 660 until the rod 660 is at the slot 666 closest to thedesired rotational orientation, and reinserting the protrusion 646.

As discussed above, the housing 650 holds the rotating magnet 652. Inthe embodiment illustrated in FIG. 6B, the rotating magnet 652 iscoupled to the drive shaft 642 in a one to one manner, such that onerotation of the rotating magnet 652 causes one rotation of the driveshaft 642. Of course, any number of gearing systems, such as or similarto those described elsewhere herein, may be interposed between therotating magnet 652 and the drive shaft 642. In that way, more turns ofthe rotating magnet 652 may be required to effectuate a full turn of thedrive shaft 642, thereby increasing the torque of the drive shaft 642 bycomparison to the rotating magnet 652.

In at least some embodiments, the device shown in FIG. 6B issubstantially bilaterally symmetrical from proximal to distal end.Therefore, the opposite elements, such as the second rod 661 and thesecond drive shaft 643, may be the same as has already been discussed.

FIG. 6C illustrates two spinal adjustment implants 620 and 621, similarto the two spinal adjustment implants 500 a, 500 b coupled bilaterallyto three lumbar vertebrae shown in FIG. 6 . The two spinal adjustmentimplants 620 and 621 share many of the same features as is describedwith respect to other embodiments disclosed herein. However, rather thanbeing attached to the three lumbar vertebrae using standard pediclescrews, as is shown in FIG. 6A, the two spinal adjustment implants 620and 621 are coupled to the three lumbar vertebrae using a different typeof specialized screw having a different head 622. As can be seen, theheads of the specialized screws 622 are facing to the rear (the same asthe pedicle screws shown in FIG. 6A) of the spine. It should beappreciated that any type of screw and head fixture may be used so longas it adequately anchors the extension rods (and therefore the spinaladjustment implants) with respect to the spine. Depending on the lengthof the extension rods being used to fix the spinal adjustment implants620 and 621 to the spine, care may need to be taken not to allow excessrod length to impinge on nervous or other critical tissues. In someembodiments, the excess length of the extension rods, on the side of thepedicle screw opposite the spinal implant, may be trimmed so that theextension rod terminates in a surface substantially flush with the outersurface of the pedicle screw housing.

While FIGS. 6A and 6C illustrate two spinal adjustment implantsbilaterally implanted next to the spine and attached to the spine usingthree extension members, each, which are, in turn, fixed to threeadjacent vertebrae using pedicle screws and housings. In those figures,the three extension members extend transversely or laterally, and thepedicle screw housings face to the rear of the patient. Stated inanother way, the pedicle screws in FIGS. 6A and 6C are inserted intotheir respective vertebrae substantially in a posterior-anteriordirection. FIG. 6D illustrates the right-lateral spinal adjustmentimplant from a more frontal viewpoint. While FIGS. 6A, 6C, and 6Dillustrate the spinal adjustment devices predominantly to the lateralsides of the lumbar spine, it should be understood that the spinaladjustment devices may be placed closer or further away from the spinalmidline laterally, or closer or further away from the spinal midlineanterior-posteriorly. This may be accomplished through selectiveplacement, including angling, of the pedicle screw as well as insertingthe extension member into one side or the other of the pedicle screwhousing.

Flexion of the first and/or second rods 558 a, 558 b, 588 a, 588 b mayincrease the amount of angle increase that can occur during compressiveadjustment. In some embodiments, smaller diameter rods are used toincrease the possible flexion. In some embodiments, rods having adiameter of less than about 6.5 mm, less than about 5.5 mm less thanabout 4.5 mm, less than about 3.5 or less than about 2.5 mm are used. Insome embodiments, rods comprise PEEK (polyether ether ketone) toincrease flexion. In some embodiments, flexible rods comprise alaser-cut structure and/or a Nitinol structure. In FIG. 7 , the lordoticCobb angle (angle of Lordosis) a between the L3 608 and L5 602 lumbarvertebrae is shown in a radiographic image of an L3-L5 fusion havingfirst and second interbody spacers 612, 614 placed between the vertebralbodies of the L3, L4, and L5 lumbar vertebrae 608, 610, 602. Someflexion of the rods 616, 618 is shown. It will be understood thatbecause the image is taken laterally, rods 616 and 618 are overlaid andthus appear to be only one rod. But, two rods are actually present. Thelordotic Cobb angle may be increased (or decreased) by about 0.5-15°,about 1-13°, about 1.5-11°, about 2-9°, about 2.5-7°, or about 3-5° perlevel through use of the spinal adjustment implants such as thosedescribed above (e.g., 500 a, 500 b) either unilaterally or bilaterallyplaced in the L3-L5 segments, for a total L3 to L5 angle increase ofabout 1-30°.

In some embodiments, one or more gear modules are placed between thedriving member 514 and one or both of the first and second threadeddrivers 528, 542, in order to increase the amount of compressive forcethat may be applied during adjustment. In some embodiments, the gearmodules comprise planetary gearing, including possibly one or more ofsun gears, ring gears and planet gears.

In some embodiments, at least one planetary gear stage (e.g., two,three, four, five, six, or even more planetary gear stages) is includedbetween (operatively coupled to both of and/or between) the permanentmagnet and the drive shaft (e.g., drive member, lead screw). Eachplanetary gear stage can comprise a sun gear and a plurality ofplanetary gears (e.g., three, four, five, six, or even more planetarygears), which are rotatably held within a frame, e.g., by pins. The sungear is either a part of the magnet housing (e.g., the sun gear may bedirectly connected to the magnet/magnet housing), or a part of the gearframe. The rotation of the sun gear causes the planetary gears to rotateand track along inner teeth of a ring gear insert (e.g., a ring gearinsert). Each gear stage has a gear reduction ratio (e.g., of 3:1, 4:1,5:1, 6:1, 7:1, 8:1, or even more), which results in a total gearreduction (e.g., a total gear reduction of 64:1—provided by threeplanetary gear stages each having a reduction ratio of 4:1). The totalreduction ratio is merely the individual reduction radios multiplied.Therefore, a planetary gear system having 4 stages, each with a ratio of3:1 would have a total reduction ratio of (3×3×3×3):(1×1×1×1), or 81:1.It should be understood that other gear reductions, and numbers ofstages may be used.

In some embodiments, a slip clutch is placed between the driving member514 and one or both of the first and second threaded drivers 528, 542,in order to set a maximum compressive force that can be applied betweenthe two drivers. In some embodiments, a differential is placed betweenthe driving member 514 and the first and second threaded drivers 528,542 to allow one of the first and second rods 558, 588 to continueadjusting after the other rod is no longer able to adjust due to havingreached a threshold resistive force. In some embodiments, thedifferential incorporates differential gears. The differential gears mayinclude, for example, bevel gears, spur gears, worm gears, and/or aTorsen-type differential—such differential gears will be discussed inmore detail, below. In some embodiments, one or more thrust bearings isincorporated in order to protect one or more of the driving member 514,slip clutch(s), gear module(s), and/or differential from excessivestresses. Such thrust bearings may be held substantially fixed withrespect to and by the walls of the housing 502, for example, by ledges,abutments, rings, or other structures incorporated into or extendingfrom the housing 502 (e.g., an inner wall of the housing).

FIG. 8 illustrates a spinal adjustment implant 500 a implanted in anL3-L5 fusion having first and second interbody spacers 612, 614 placedbetween the L3 and L4, and L4 and L5 lumbar vertebrae 608, 610, 602,respectively. All of the connections between the rods, extension membersand pedicle screws are shown in FIG. 8 as being fixed. Non-invasiveactuation and rotation of the driving member 514 (depending on thethread handedness, in the first rotational direction 556 or the secondrotational direction 559 (FIG. 3A)) increases compression, e.g., alongline C. In combination with flexion of the first and/or second rods, thecompressive forces can decrease dorsal distance Dd more than anteriordistance Da thereby advantageously increasing the lordotic Cobb angle.

FIG. 9 illustrates an embodiment of a spinal adjustment implant 700. Thespinal adjustment implant 700 is similar to the implant 500 of FIGS.1-3C and 500 a of FIG. 8 , but additionally includes a first pivotableinterface 729 between the first rod 758 and pedicle screw 725 and asecond pivotable interface 727 between the second rod 788 and pediclescrew 723. Examples of such pivotable interfaces will be discussed inadditional detail below, for example with respect to FIGS. 45A-48 . Suchpivotable interfaces allow the pedicle screws and the vertebrae to whichthey are attached to change angle more easily; consequently, to decreaseDorsal distance Dd more than Anterior distance Da the spinal adjustmentimplant need not rely on only potential or minor flexion in theextension rods and/or pedicle screws. The first and second pivotableinterfaces 729, 727 may allow a potentially greater increase in thelordotic Cobb angle during compression than that permitted by the spinaladjustment implant 500 a of FIG. 8 (which lacks pivotable interfaces729, 727).

When the magnitude of compression force C is increased by the spinaladjustment implant 700, the L5 lumbar vertebra 602 is able to rotateaccording to or along arc R1 with respect to an axis of rotation 719 ofthe first pivotable interface 729. Likewise, the L3 lumbar vertebra 608is able to rotate according to or along arc R2 with respect to an axisof rotation 721 of the second pivotable interface 727. In someembodiments, the first and second pivotable interfaces 729, 727 arelockable and unlockable to allow free rotation about the axes ofrotation 721, 719 during adjustment and to inhibit rotation about theaxes of rotation 721, 719 after adjustment is complete. In someembodiments, the first and second pivotable interfaces 729, 727 arenon-invasively lockable and unlockable (such as by using a magneticfield to lock and unlock or by using an electromagnetic signal, such asRF, Bluetooth, etc.). In some embodiments the first and second pivotableinterfaces 729, 727 are configured to be non-invasively lockable andunlockable as part of the non-invasive adjustment. In some embodimentsthe first and second pivotable interfaces 729, 727 are configured to benon-invasively lockable and unlockable in conjunction with the rotationof the driving member 514. In some embodiments, the pivotable interfaces729, 727 are configured to be intermittently locked and unlocked duringan adjustment procedure.

In some embodiments, one or more of the pivotable interfaces isconfigured to rotate freely in either direction (e.g., clockwise and/orcounterclockwise). In some embodiments, one or more of the pivotableinterfaces is partially constrained to have free rotation in onedirection but no rotation in the other direction—this may beaccomplished using a free wheel or other one-way clutching. Examples ofdevices that may be used to allow unidirectional rotational movement areprovided below—in some embodiments, a clutch system, ratchet system, orother motion inhibiting device may be used. In some embodiments, thepivotable interfaces include two-way locking so that they may lock andunlock automatically by the operation of the spinal adjustment implant.For example, the External Remote Controller (ERC) may be used to lockand unlock a magnetic lock which is capable of reversibly removing therotational freedom of the pivotable interface(s). An example of one suchdevice is shown in FIG. 48 . In some embodiments which may be eitherfreely rotating or lockable, there may additionally by constrainedrotation or motion, wherein there are limits, extents, or detents thatlimit the total amount of travel of a particular rotation or motion. Insome embodiments, structural motion limiters may be set prior toimplantation. For example, the implanting surgeon might evaluate thepatient's spine and determine that a maximum correction of 10 degreesper pivotable interface (for a total correction of 20 degrees) is allthat is needed and/or permissible. In that case, the surgeon may seteach physical motion limiter to “10 degrees” (for example, the pivotableinterface may have markings or holes identifying the maximum angle ofrotation to which the surgeon may move the physical motion limiter).While 10 degrees was used as an example, it should be understood, thatany degree may be use—however, physically, the range of correction willgenerally be less than about 30, less than about 25, less than about 20,less than about 15, less than about 10, or even less than about 5degrees per pivotable interface.

FIGS. 10-12 illustrate a spinal adjustment implant 800 for implantationalong the spine of a subject. The spinal adjustment implant 800comprises a housing 802 having a first end 804 and a second end 806. Thehousing 802 includes a cavity 808, which extends between the first end804 of the housing 802 and the second end 806 of the housing 802. Thecavity 808 may have a variable inner diameter along its length or mayhave a generally constant inner diameter. The inner wall 810 of thehousing 802 may have circumferential grooves or abutments 812, in orderto axially maintain certain elements of the assembly. A driving member814 is rotatably disposed within the cavity 808. The driving member 814may comprise any non-invasively rotatable element, such as thosedescribed with respect to FIGS. 13-16 . The embodiment of the drivingmember 814 illustrated in FIG. 12 comprises a cylindrical,radially-poled permanent magnet 816 secured within a first magnethousing 818 and a second magnet housing 820.

In the embodiment of FIGS. 10-12 , the driving member 814 is positionedlongitudinally between two abutments 812 by two radial bearings 824,which facilitate free rotation of the driving member 814 about a drivingmember axis 826. A first threaded driver 828 has a first end 830 havinga shaft 832, and the first magnet housing 818 has a cylindrical cavity838. A first clutch 836 engages the inside of the cylindrical cavity838, and inner cavity of the first clutch 836 engages the shaft 832 ofthe first threaded driver 828. The first clutch 836 is configured tocouple rotational motion between the first magnet housing 818 and thefirst threaded driver 828 in a first rotational direction 856 when thefirst magnet housing 818 is turned by the radially-poled permanentmagnet 816 in a first rotational direction 856. But, the first clutch836 is configured to cause slippage between the first magnet housing 818and the first threaded driver 828 when the first magnet housing 818 isturned by the radially-poled permanent magnet 816 in a second rotationaldirection 859 (e.g., opposite the first rotational direction 856).

A second clutch 842 engages the inside of the cylindrical cavity 844 ofthe second magnet housing 820, and inner cavity of the second clutch 842engages the shaft 846 of the second threaded driver 850. The secondclutch 842 is configured to couple rotational motion between the secondmagnet housing 820 and the second threaded driver 850 in the secondrotational direction 859 when the second magnet housing 820 is turned bythe radially-poled permanent magnet 816 in the second rotationaldirection 859. But, the second clutch 842 is configured to causeslippage between the second magnet housing 820 and the second threadeddriver 850 when the second magnet housing 820 is turned by theradially-poled permanent magnet 816 in the first rotational direction856.

Incorporation of one-way clutches (e.g., one way clutches 836, 842) mayallow the driving member 814 to be capable of independently drivingeither the first threaded driver 828 or the second threaded driver 850depending on which direction (e.g., first rotational direction 856 orsecond rotational direction 859) the driving member 814 is caused toturn. In some embodiments, the first and second clutches 836, 842comprises a number of different types of one-way clutching, includingbut not limited to a needle clutch, a free wheel, a sprag clutch, aspring clutch, a face gear, or a ratchet. In some embodiments, theradial bearings or thrust bearings are themselves be configured asone-way clutches (e.g., as a hybrid component). Indeed, any of a numberof different clutch mechanisms may be used as the one-way clutches 836,842. Additional examples are discussed in greater detail, below, withrespect to at least FIGS. 40A-40C.

The first and second threaded drivers 828, 850 have second ends 858, 860having male threads 862, 864, which engage female threads 866, 868 offirst and second rods 870, 872. In some embodiments, the spinaladjustment implant 800 is configured for compression (i.e., the threadsof both of the first and second threaded drivers 828, 850 and the femalethreads 866, 868 are right-handed). In other embodiments, the spinaladjustment implant 800 is configured for tension/distraction (i.e., thethreads of both of the first and second threaded drivers 828, 850 andthe female threads 866, 868 are left-handed).

Extension members 874, 876, 878 may be configured to couple to the firstrod 870, second rod 872 and housing 802, respectively. The extensionmembers 874, 876, 878 may be coupled to pedicle screws (not shown).These extension members may be the same as the many other extensionmembers discussed in detail above.

While some illustrated embodiments provide instrumentation to two lumbarlevels (L3-L4 and L4-L5), one level only of instrumentation, or greaterthan two levels of instrumentation are also within the scope ofembodiments of the present invention. Indeed, embodiments of the systemsfor spinal adjustment (including spinal adjustment implants) disclosedherein may have one driving system (e.g., lead screws and permanentmagnet, etc.), or more than one driving system. The systems for spinaladjustment disclosed herein may be attached to two vertebrae, to threevertebrae, to four vertebrae, to five vertebrae, to six vertebrae oreven more vertebrae, as needed. Regardless, of the number of vertebraeto which the system for spinal adjustment is attached, the device may bea single device, attached to the vertebrae at various points (e.g., thesystems shown in FIGS. 1-3 and/or 10-12 )—of course, the device may haveone or more than one complete drive system. Alternatively, the systemfor spinal adjustment may be modular, so that multiple (e.g., more thanone), smaller devices may be connected to the desired vertebrae (e.g.,the system shown in FIG. 20 )—these devices will generally, but notalways, have their own, unique drive systems (e.g., one drive system permodular portion). As will be readily apparent, because the extensionmember's attachment rings (having the set screw) may be moved up anddown the rods and or the housing, the vertebrae to which the extensionmembers are attached may be adjacent, separated by one or morevertebrae, or a combination of the two.

Besides degenerative disc disease, degenerative deformity patients(adult scoliosis, complex spine) may also be treated with spinaladjustment implants as disclosed herein. Embodiments of the spinaladjustment implants disclosed herein may be used for initial fusionsurgery, or in revision surgeries. Embodiments of the spinal adjustmentimplants disclosed herein may be used to instrument only particularlevels of the lumbar vertebrae or vertebrae of other sections of thespine. Embodiments of the spinal adjustment implants disclosed hereinmay be implanted using minimally invasive surgery (MIS) techniques, forexample, using medial placement through a mid-line incision or byplacement through small incisions using endoscopes or even operatingmicroscopes.

FIGS. 13-16 illustrate embodiments of alternate sources to thecylindrical, radially-poled permanent magnet 516 as the driving member514 of a spinal adjustment implant 500, 700, 800. FIG. 13 illustrates anon-invasively adjustable system 1300 comprising an implant 1306 havinga first implant portion 1302 and a second implant portion 1304, thesecond implant portion 1304 non-invasively displaceable with relation tothe first implant portion 1302. The first implant portion 1302 issecured to a first bone portion 197 and the second implant portion 1304is secured to a second bone portion 199 within a patient 191. A motor1308 is operable to cause the first implant portion 1302 and the secondimplant portion 1304 to displace relative to one another. An externalremote controller (ERC) 1310 has a control panel 1312 for input by anoperator, a display 1314 and a transmitter 1316. The transmitter 1316sends a control signal 1318 through the skin 195 of the patient 191 toan implanted receiver 1320. Implanted receiver 1320 communicates withthe motor 1308 via a conductor 1322. The motor 1308 may be powered by animplantable battery, or may be powered or charged by inductive coupling.

FIG. 14 illustrates a non-invasively adjustable system 1400 comprisingan implant 1406 having a first implant portion 1402 and a second implantportion 1404, the second implant portion 1404 non-invasivelydisplaceable with relation to the first implant portion 1402. The firstimplant portion 1402 is secured to a first bone portion 197 and thesecond implant portion 1404 is secured to a second bone portion 199within a patient 191. An ultrasonic motor 1408 is operable to cause thefirst implant portion 1402 and the second implant portion 1404 todisplace relative to one another. An external remote controller (ERC)1410 has a control panel 1412 for input by an operator, a display 1414and an ultrasonic transducer 1416, which is coupled to the skin 195 ofthe patient 191. The ultrasonic transducer 1416 produces ultrasonicwaves 1418 which pass through the skin 195 of the patient 191 andoperate the ultrasonic motor 1408.

FIG. 15 illustrates a non-invasively adjustable system 1700 comprisingan implant 1706 having a first implant portion 1702 and a second implantportion 1704, the second implant portion 1704 non-invasivelydisplaceable with relation to the first implant portion 1702. The firstimplant portion 1702 is secured to a first bone portion 197 and thesecond implant portion 1704 is secured to a second bone portion 199within a patient 191. A shape memory actuator 1708 is operable to causethe first implant portion 1702 and the second implant portion 1704 todisplace relative to one another. An external remote controller (ERC)1710 has a control panel 1712 for input by an operator, a display 1714and a transmitter 1716. The transmitter 1716 sends a control signal 1718through the skin 195 of the patient 191 to an implanted receiver 1720.Implanted receiver 1720 communicates with the shape memory actuator 1708via a conductor 1722. The shape memory actuator 1708 may be powered byan implantable battery, or may be powered or charged by inductivecoupling.

FIG. 16 illustrates a non-invasively adjustable system 1800 comprisingan implant 1806 having a first implant portion 1802 and a second implantportion 1804, the second implant portion 1804 non-invasivelydisplaceable with relation to the first implant portion 1802. The firstimplant portion 1802 is secured to a first bone portion 197 and thesecond implant portion 1804 is secured to a second bone portion 199within a patient 191. A hydraulic pump 1808 is operable to cause thefirst implant portion 1802 and the second implant portion 1804 todisplace relative to one another. An external remote controller (ERC)1810 has a control panel 1812 for input by an operator, a display 1814and a transmitter 1816. The transmitter 1816 sends a control signal 1818through the skin 195 of the patient 191 to an implanted receiver 1820.Implanted receiver 1820 communicates with the hydraulic pump 1808 via aconductor 1822. The hydraulic pump 1808 may be powered by an implantablebattery, or may be powered or charged by inductive coupling. Thehydraulic pump 1808 may alternatively be replaced by a pneumatic pump.

Though not illustrated, another driving element 242 may include amagneto restrictive element. A number of materials may be used toproduce the components like the housing, first distraction rod, seconddistraction rod, first lead screw, and second lead screw, including butnot limited to titanium, titanium alloys, titanium 6-4, cobalt-chromiumalloys, and stainless steel. The threads on the lead screw in someembodiments may comprise Acme threads, square threads or buttressthreads. A number of other possible driving systems are discussed insome detail below.

FIGS. 17-18 illustrate an implant system 1000 comprising a spinaladjustment implant 1002, first pedicle screw 1004 and second pediclescrew 1006. The spinal adjustment implant 1002 includes a housing 1008,which may comprise a first housing portion 1010 and a second housingportion 1012, joined together at a joint 1014 (e.g., similar to thejoint described with respect to FIG. 6B). The joint may be a weld joint,adhesive joint, threaded joint, or other type of joint. Alternatively,the housing 1008 may be constructed of a single, monolithic structure,as described in U.S. Pat. No. 9,179,938, which is incorporated byreference herein in its entirety. In certain embodiments, the housing1008 is coupled at a first end 1016 to a base 1018 having a rod 1020. Insome embodiments, housing 1008 is fixedly coupled to the base 1018. Inother embodiments, as will be discussed below, the housing 1008 ismovably couple to the base 1018, so as to, for example, allow pivotingmovement or to allow further distraction/retraction capability (throughthe addition of another drive system, or the incorporation of anotherdrive member into the currently present drive system). While certainfeatures of the rod 1020 are described below, it should be understoodthat any modification of this general structure is contemplated by thisdisclosure.

The rod 1020 may extend in a generally parallel direction to the housing1008, and be offset from the housing by a distance D. Alternatively, therod 1020 may extend directly along the longitudinal axis of the housing.The rod 1020 is shown as extending alongside the housing on the sameside as the rod 1040. In some embodiments, the rod 1020 and the rod 1040are not aligned with each other. In some embodiments, the rod 1020 andthe rod 1040 are offset by an angle in the range of about 1-180 degrees,about 5-160 degrees, about 10-140 degrees, about 15-120 degrees, about20-100 degrees, about 25-80 degrees, and about 30-60 degrees or anyother degree of offset that may be advantageous—it will be understoodthat such an offset may be advantageous for applications related to thespine, or applications related to other portions of the skeletal system.The rod 1020 is configured for securement to the second pedicle screw1006, having a threaded shank 1022 a head 1024 and a tightening nut1026. While a pedicle screw is described, one of ordinary skill in theart will readily understand that any of a number of systems may be usedto fix the rod 1020 to the body of a patient, for example the skeletalsystem (e.g., a ring and extension member-based system, such asdisclosed elsewhere herein).

A rod 1028 (which may share one or more characteristics with rod 1020,just described) is configured to be telescopically moveably into and outof (e.g., moveable/translatable relative/with respect to) an interior1030 of the housing 1008 at a second end 1036 thereof. The rod 1028 mayinclude one or more longitudinal grooves 1032 which may be engaged by aninsert 1034 within the housing 1008, thus allowing longitudinaldisplacement between the housing 1008 and the rod 1028, but stopping anysignificant rotation between the housing 1008 and the rod 1028 (thisanti-rotation member may function substantially the same as wasdescribed above with respect to other embodiments). The rod 1028 may becoupled to a base 1038 having a rod 1040, which may extend in agenerally parallel direction to the housing 1008 and/or the rod 1028.The base 1038 may be coupled to the rod 1028 by welding, or by a screw1029. Alternatively, the base 1038 is pivotably coupled to the rod 1028so that some rotational movement is allowed between the two at theconnection of the two (other types of pivotable/moveable joints arecontemplated, such as those that allow unidirectional motion, and/orthose that allow movement in more than a single plane (i.e., rotationalmovement only)). In other embodiments, as will be discussed below, therod 1028 is movably couple to the base 1038, so as to, for example,allow pivoting movement or to allow further distraction/retractioncapability (through the addition of another drive system, or theincorporation of another drive member into the currently present drivesystem).

The rod 1040 may be configured for securement to the first pedicle screw1004, which may include similar components as the second pedicle screw1006. In use, the first pedicle screw 1004 is engaged into a firstvertebra, and the second pedicle screw is engaged into a secondvertebra. While a pedicle screw is described, one of ordinary skill inthe art will readily understand that any of a number of systems may beused to fix the rod 1040 to the body of a patient, for example theskeletal system (e.g., a ring and extension member-based system, such asdisclosed elsewhere herein). In some cases, the first and secondvertebrae may be adjacent each other. In other cases, the first andsecond vertebrae may have one or more intervening vertebrae.

The spinal adjustment implant 1002 is configured to be non-invasivelyshortened or lengthened, in order to move a first and second vertebrawith respect to each other. A magnet 1042 (for example, a radiallypoled, cylindrical magnet) may held within a casing 1046 which isrotatably held within the housing 1008 by a radial bearing 1044. A pin1048 at one end of the casing 1046 may be insertable within (e.g., heldby) an inner bore 1050 of the radial bearing 1044. One or more planetarygear modules 1052, 1054 (such as those discussed above), may couple themagnet 1042 and casing 1046 to a lead screw (e.g., drive member, driveshaft, drive element, etc.) 1056. A thrust bearing 1058 may be securedwithin the housing 1008 to protect the planetary gear modules (orstages) 1052, 1054 and the magnet 1042 from axial compressive (and/ortensile) stresses.

The lead screw 1056 may be coupled to the gear modules 1052, 1054 or themagnet 1042 (of course, it will be understood that gearing increases thepossible torque of the system and therefore the possible force that canbe generated by the system). In some embodiments, the lead screw isconnected to the gear modules or the magnet using a coupler 1057 thatallows some amount of axial play (as discussed above), such as by a pin1060. The rod 1028 may have a hollow interior 1062, which may containthreads. In some embodiments, the hollow inter 1062 itself is threaded.Alternatively, the hollow interior 1062 may contain a nut 1064 having afemale thread 1066 (e.g., the nut may be fixedly bonded to the innersurface of the hollow interior 1062). The external threads of the leadscrew 1056 engage the female thread 1066 of the nut 1064, thus allowingmovement of the rod 1028 and the housing 1008 towards each other or awayfrom each other, depending on the direction that the lead screw 1056 isturned. The pieces of the system 1000 may be sealed in any of a numberof ways to keep out bodily fluids and to keep in any fluids contained bythe device (e.g., lubricants or other fluids). Any of the sealsdiscussed elsewhere herein may be used here as well. For example, ano-ring 1068 may be held within a circumferentially extending groove 1070in the rod 1028 to provide a dynamic seal against an inner surface 1072of the housing 1008 (of course, the groove may be in the inner surfaceof the housing as opposed to the outer surface of the rod). A movingmagnetic field, for example, applied non-invasively by the ExternalRemote Controlled (ERC) 180 of FIGS. 4-5 , may be used in a patient(including but not limited to a conscious patient) to change the lengthof the spinal adjustment implant 1002, thus changing the distance and/orangle between the first vertebrae and the second vertebrae,

Implant system 1000 has been described as having an axially asymmetricdrive system. That is to say that, by contrast to the device shown inFIG. 6B, the implant system 1000 has a drive shaft on only one side ofthe spinning magnet. This means that only one end of the implant system1000 may extend or retract from within the housing. In some embodiments,that is sufficient.

However, in other embodiments, the housing contains a bilaterallysymmetrical drive system, including, for example, one magnet, two gearsystems, and two drive shafts (as will be easily understood in view ofthe disclosure presented herein).

FIG. 19 illustrates a cross-sectional view of the system 1000 shown inFIG. 18 , but rotated approximately 90 degrees clockwise. FIG. 20illustrates two systems, such as the system 1000 of FIGS. 18-19 attachedto the spinal column in a modular fashion at a joint (which may also beattached to the spinal column). The two devices are secured to thespinal column in series, with a shared base between them. The telescopicrods of each of the implants are secured to the shared base.

FIGS. 21A-21D and FIGS. 22A-22E illustrate an embodiment of the spinaladjustment implant 2100 for implantation along the spinal system of asubject. The spinal adjustment implant 2100 is similar to the implant700 of FIG. 9 as it provides pivotable interfaces that may allow apotentially greater increase in the lordotic Cobb angle duringcompression than that permitted by the spinal adjustment implant 500 aof FIG. 8 . As will be discussed in more detail below, the drivingmember of the spinal adjustment implant 2100 can be rotated to generatea compression force that allows a first attached vertebra to rotate withrespect to a second attached vertebra.

In some embodiments, the spinal adjustment implant 2100 comprises adriving member that is rotatably coupled to a plurality of gears. Insome embodiments, the plurality of gears is coupled to a linkage systemthat can be coupled to a plurality of vertebra. As the driving member isrotated, the plurality of gears translates the rotational motion tocause the linkage system to pivot about center of rotation which cancause one of the attached vertebrae to rotate about the center ofrotation.

FIGS. 21A-22E generally illustrate an embodiment which may use a motoror magnet or alternative non-invasively operable drive system to turn aworm (labeled as “worm gear” in provisional) which is engaged to a wormwheel, which moves a link in order to change the distance and/or anglebetween two rods (red and green) to which pedicle screws may be secured.FIG. 21A illustrates an embodiment of the spinal adjustment implant2100. In some examples, the spinal adjustment implant 2100 can furtherinclude a housing system (not pictured) that can be disposed about thesurface of the spinal adjustment implant 2100. The spinal adjustmentimplant 2100 can include a driving member 2114 having a first end 2106and a second end 2104. The driving member 2114 may comprise anynon-invasively rotatable element, such as a magnet.

In some embodiments, the driving member 2114 can be disposed about afirst rod 2170 that extends from the first end 2106 and is rotationallycoupled to a gear system 2120. In some embodiments, the gear system 2120can be a planetary or a harmonic drive. As the driving member 2114 isrotated, the rotation is translated to the gear system 2120. In someembodiments the gear system 2120 can provide a high gear reduction ratioin a limited space. As the driving member 2114 rotates, the rotationcauses the gear system 2120 to rotate.

As illustrated in FIG. 21A, the gear system 2120 can be coupled to asecond rod 2136 that is coupled to a worm drive 2130. FIG. 21C providesa side view of the worm drive 2130. In some embodiments, the worm drive2130 includes a worm screw 2132 and a worm wheel 2134. The worm drive2130 can provide large gear reductions. As well, in some embodiments,the worm drive 2130 can provide a locking feature which can act as abrake to ensure that the worm wheel 2134 does not unintentionally causethe worm screw 2132. As illustrated in FIG. 21C, in some embodiments,the worm screw 2132 is disposed about the second rod 2136 and isthreaded to engage with the worm wheel 2134. As discussed above, as thedriving member 2114 is rotated, the rotation is translated to the gearsystem 2120 through the first rod 2170. The gear system 2120 can thencause the rotation of the worm drive 2130 which engages with the wormwheel 2134.

In some embodiments, the worm drive 2130 may engage a linkage system2105 which can cause the rotation of an attached vertebra. FIGS. 21B-21Cillustrate two side views of the spinal adjustment implant 2100 engagedwith the linkage system 2105. In some embodiments, the linkage systemcan include a driven link 2140, a coupler link 2150, and a ground link2160. In some examples, the worm wheel 2134 of the worm drive 2130 hasan extended portion (not illustrated) that engages with a portion of thedriven link such that rotation of the worm wheel 2134 can cause rotationof the driven link 2140. As will be discussed below, the driven link2140 can be movably coupled with the coupler link 2150 to cause aportion of the coupler link 2150 to pivot in a first direction as thedriver link 2140 rotates. The coupler link 2150 can be further securedto a ground link 2160 which allows a first attached vertebra to rotatewith respect to a second attached vertebra.

In some embodiments, the driven link 2140 can be movably coupled to thecoupler link 2150 through the engagement portion 2142 of the driven link2140. The engagement portion 2142 of the driven link 2140 can bedisposed about the protrusion 2151 of the coupler link 2150. A first endof the protrusion 2151 of the coupler link 2150 can be seen in FIG. 21Cwith the driven link 2140 disposed about it. As will be discussed inmore detail below, as the driven link 2140 is rotated, this can cause aportion of the coupler link to pivot.

The coupler link 2150 can comprise a plurality of components. Asillustrated in FIG. 21A-21B, in some embodiments, the coupler link 2150can include a first body 2152, a second body 2143, and a coupler rod2156. As discussed above, a first end of the first body 2152 of thecoupler link 2150 can include a protrusion 2151 that is disposed withinan engagement portion of the driven link 2140 and is movably coupledsuch that rotation of the driven link 2140 can cause the first body 2152of the coupler link 2150 to pivot. The second end of the first body 2152of the coupler link 2150 can be movably engaged with the second body2158 of the coupler link 2150. A coupler rod 2156 can extend from thesurface of the second body 2158 to engage with a first vertebra. In someembodiments, as illustrated in FIG. 21A, the coupler rod 2156 can have abase portion 2154 that is movably coupled with the second body 2158. Thebase portion 2154 can be circular and disposed within an opening in thesecond body 2158. The second body 2158 of the coupler link 2150 canfurther include a protrusion 2153 that is movably coupled with theground link 2160 at the engagement portion 2166. A first end of theprotrusion 2153 of the ground link 2160 can be seen in FIG. 21C with theground link 2160 disposed about it. As will be discussed in more detailbelow, the movable connection between the ground link 2160 and thesecond body 2158 of the coupler link 2150 can cause the second body 2158to rotate about the engagement portion 2166.

The ground link 2160 can anchor the spinal adjustment implant 2100 to asecond vertebra to provide for the rotation of the first vertebraattached to the coupler rod 2156 of the coupler link 2150. In someembodiments, the ground link 2160 can include a body 2162, a jointportion 2168, and a ground rod 2164. As illustrated in FIGS. 21A-21B,the body 2162 of the ground link 2160 can include a first end thatincludes an engagement portion 2166 that is movably engaged with thejoint portion 2168, and a portion of the second body 2158 of the couplerlink 2150. The body 2162 of the ground link 2160 can further include theground rod 2164 that extends from a surface of the body 2162 at thesecond end. In some embodiments, the ground rod 2164 can extend from thesurface of the second body 2158 to engage with a second vertebra. Insome embodiments, the ground rod 2164 is anchored to the second vertebrato secure the spinal adjustment implant 2100 as the first vertebra isrotated.

FIG. 21D illustrates the center of rotation 2180 of the spinaladjustment implant 2100. As discussed above, the rotational movement ofthe driving member 2114 is translated to a rotation of the driven linkthrough the gear system 2120 and the worm drive 2130. As the driven link2140 is rotated in a first direction, this can cause the first body 2152of the coupler link 2150 to pivot in a first direction. This pivotingmotion is translated to the second body 2158 of the coupler link 2150and the attached first vertebra attached to the coupler rod 2156. Asmentioned above, the body 2162 of the ground link 2160 is secured to asecond vertebra. The second body 2158 is movably attached to a first endof the body 2162 of the ground link 2160 such that the second body 2158can rotate about the engagement portion 2166 of the body 2162, causingthe first vertebra to rotate in a first direction relative to the secondvertebra.

FIGS. 22A-22E illustrates an example of the rotation of a first vertebraas a result of the rotation of the driving member 2114. FIG. 22Aillustrates the spinal adjustment implant 2100 secured to a firstvertebra 2191 and a second vertebra 2192 using a plurality of attachmentsystems 2193, 2194. In some embodiments, the attachment systems caninclude one or more of: a pedicle screw, hook, or a wire. As shown inFIG. 22A, the coupler rod 2156 is secured to the first vertebra 2191using the attachment system 2193 and the ground rod 2164 is secured tothe second vertebra 2192 using the attachment system 2194.

FIGS. 22B-22C illustrate the position of the first vertebra 2191 andsecond vertebra 2192 as the driving member 2114 is rotated. FIG. 22Billustrates the position of the first vertebra 2191 before the drivingmember 2114 is rotated. As can be seen, a distance exists between thefirst vertebra 2191 and the second vertebra 2192. FIG. 22C illustratesthe position of the first vertebra 2191 after the driving member 2114 isrotated. As illustrated, the first vertebra 2191 is rotated such that itis in close proximity with the second vertebra. FIGS. 22D-22E illustratea close up view of the linkage system of the spinal adjustment implant2100 before and after the driving member 2114 is rotated. As seen inFIG. 22E, the rotation of the driving member 2114 rotates the worm drive2130 such that the driven link 2140 pivots in a first direction and thecoupler link 2150 rotates in a first direction about the center ofrotation 2180. The rotation of the coupler link 2150 rotates theattached first vertebra 2191 such that the distance between the firstvertebra 2191 and the second vertebra 2192 is reduced.

FIGS. 23A-23C generally illustrate an embodiment using differentialgearing, including one or more sun gears and planetary gears, toincrease the amount of force that can be placed on the vertebrae duringadjustment (e.g., compression) via relatively high gear ratios. Thecompact packaging of the gears increases the efficiency of the torque,and thus force, that can be delivered within a small profile implant.FIGS. 23A-C illustrate a spinal adjustment implant 2300 for implantationalong the spinal system of a subject. In some cases, the subject may bea patient having degenerative disc disease that necessitates fusion ofsome or all of the lumbar vertebrae through fusion surgery. The spinalimplant 2300 is configured to be used in place of traditional rods,which are used to maintain posterior decompression and stabilize duringfusion surgery. Some embodiments of the spinal implant 2300 arecompatible with interbody spacers placed between the vertebrae beingtreated. The spinal adjustment implant 2300 may comprise a housing 2302which includes a first end and a second end. The housing 2302 includes acavity 2304 which may be substantially similar to the cavities describedin other embodiments disclosed herein. The cavity 2304 may includeelements configured to maintain certain elements of the assembly withinthe housing 2304, for example, protrusions, grooves, or abutments. Thehousing 2302 may be made from materials which are biocompatible andwhich may allow for relatively small wall thicknesses while maintainingthe structural integrity of the housing 2302 when in use. For example,the housing 2302 may comprise titanium alloys, ceramics and/orbiocompatible polymers. Various sizes and shape of the housing 2302 areexpressly contemplated, although preferably the housing 2302 is sized tobe implanted within the body of a patient. For example, in theembodiments illustrated in FIGS. 23A-C the housing 2302 comprises acylindrical shape, can have an outer diameter of about 10 mm, and canhave a length of about 45 mm. In some embodiments the housing 2302 maybe from about 20 mm to about 70 mm long, from about 30 mm to about 60 mmlong, or from about 40 mm to about 50 mm long. In some embodiments thehousing 2302 may have a diameter from about 5 mm to about 20 mm, fromabout 7 mm to about 15 mm, or from about 9 mm to about 11 mm.

A driving member 2306 is rotatably disposed within the cavity 2304 ofthe housing 2302. The driving member 2306 may comprise anynon-invasively rotatable element, for example a rotatable element thatis substantially similar to rotatable elements described in otherembodiments disclosed herein. The particular embodiment of the drivingmember 2306 illustrated in FIGS. 23A-C comprises a cylindrical,radially-poled permanent magnet 2308 that is secured within the cavity2304. The magnet 2308 is disposed in the cavity 2304 such that themagnet 2308 is free to rotate about a central axis 2310 within thecavity 2304. The magnet may be secured within the cavity by meanssubstantially similar to those means described in other embodimentsdisclosed herein. It is contemplated that the magnet 2308 may comprise avariety of shapes and sizes. In the embodiment illustrated in FIGS.23A-C the magnet comprises a cylindrical shape. The magnet 2308 is sizedto fit within the cavity 2304. In some embodiments the magnet 2308 maybe about 9.5 mm in diameter and about 21 mm long. In some embodimentsthe magnet 2308 may have a diameter from about 5 mm to about 20 mm, fromabout 7 mm to about 15 mm, or from about 9 mm to about 11 mm. In someembodiments the magnet 2308 may be from about 10 mm to 30 mm long, fromabout 15 mm to about 25 mm long, or from about 17.5 mm to about 22.5 mmlong.

The spinal adjustment implant 2300 can include at least a firstrotatable driver 2312 which includes a hole that comprises a femalethreaded portion 2314. In the embodiment illustrated in FIGS. 23A-C thedriving member 2306 includes a first driver 2312 and a second driver2316. The second driver 2316 can be substantially identical to the firstdriver 2312 and can include a hole that comprises a female threadedportion 2318. In some embodiments the first and second drivers 2312,2316 can be coupled to the driving member 2306 by means substantiallysimilar to those described in embodiments disclosed herein. In someembodiments a first rod 2320 has a first end comprising a male threadedportion 2322 and a second end 2324 configured to be coupled to a portionof the skeletal system. In some embodiments the second end 2324 of thefirst rod 2320 is configured to be coupled to a first portion of thespinal system via means substantially similar to those described inembodiments disclosed herein. The first portion of the spinal system maybe a first vertebra. For example, the second end 2324 of the first rod2320 may be coupled to the first vertebra by a first extension member2326, or directly via one or more of: a pedicle screw; hook; wire; orother attachment system. The first extension member 2326 may besubstantially similar to an extension member described in otherembodiments disclosed herein. The first extension member 2326 may extendgenerally transversely in relation to the housing 2302 and/or first rod2320. The first extension member 2326 may be coupled to a first vertebradirectly, via one or more of: a pedicle screw; hook; wire; or otherattachment system. In some embodiments, for example the embodimentillustrated in FIGS. 23A-23B, a second rod 2328 may be substantiallysimilar to the first rod 2320. The second rod 2328 may comprise a firstend comprising a male threaded portion 2330 and a second end 2332configured to be coupled to a portion of the skeletal system, forexample a second vertebra. The second rod 2328 may be secured to thesecond vertebra by a second extension member 2334. The second extensionmember 2334 may be coupled to the second vertebra directly, via one ormore of: a pedicle screw; hook; wire; or other attachment system.

Referring to FIG. 23B, the female threaded portion 2314 of the firstdriver 2312 and the male threaded portion 2322 of the first rod 2320threadingly engage each other such that rotation of the first driver2312 causes the first rod 2320 to move along a first longitudinal axis2336 (FIG. 23A) in a first longitudinal direction 2338. The femalethreaded portion 2318 of the second driver 2316 and the male threadedportion 2330 of the second rod 2328 threadingly engage each other suchthat rotation of the second driver 2316 causes the second rod 2328 tomove along a second longitudinal axis 2340 (FIG. 23A) in a secondlongitudinal direction 2342. Although the drivers 2312, 2316 aredescribed as comprising female threaded portions 2314, 2318 which engagewith male threaded portions 2322, 2330 of the rods, in some embodimentsthe drivers 2312, 2316 may comprise male threaded portions and the rodsmay comprise corresponding female threaded portions.

The spinal adjustment implant 2300 may additionally comprise a gearmodule or modules which can be placed between the driving member 2306and one or both of the first and second threaded drivers 2312, 2316. Insome embodiments one or both of the threaded drivers 2312, 2316 maycomprise a gear including a plurality of teeth positioned around anouter edge of the driver and configured to engage with the gear modules.For example, each of the first and second drivers 2312, 2316 maycomprise 32 teeth. In some embodiments the drivers 2312, 2316 may eachcomprise from 20 to 40 teeth, from 10 to 80 teeth, or more than 80teeth. As shown in FIGS. 23A-23C, the first driver 2312 comprises 32teeth which are configured to engage with the first gear module 2344.The gear module 2344 may comprise a gear train which can provide a highgear reduction between the driving member 2306 and the first driver2312. A high gear reduction, or step-down, allows for a relatively smalltorque generated by the driving member 2306 to be amplified, therebyallowing the first driver 2312 to apply high force to the first rod2320. For example, in some embodiments the gear reduction between thedriving member 2306 and the drivers 2312, 2316 may be about 4:1. In someembodiments the gear reduction ratio may be greater than 1:1, forexample 2:1, 4:1, 8:1, 16:1 or more. The gear module or modules cancomprise planetary gearing, including sun gears, ring gears and planetgears. In some embodiments the gear module may comprise differentialgears. The differential gears may include, for example, bevel gears,spur gears, worm gears, and/or a Torsen-type differential.

Referring to FIGS. 23B-23C, the first gear module 2344 may comprise afirst grouping of gears 2346, 2348 which are positioned at a first endof the rotatable element, for example the magnet 2308 of the drivingmember 2306. Although the embodiment illustrated in FIGS. 23A-23Cincludes two gears 2346, 2348 positioned at the first end of the magnet2308, it is expressly contemplated that the first grouping of gears maycomprise more or fewer gears, for example, one gear, three gears, fourgears, five gears, or more. The gears 2346, 2348 of the first groupingof gears are radially arranged around the central axis 2310 of themagnet 2308. The gears 2346, 2348 may comprise, for example, ten teeth.In some embodiments the gears 2346, 2358 may comprise more or fewerteeth, for example, from five to thirty, from seven to twenty, or fromten to fifteen teeth. The gears 2346, 2348 engage with a second groupingof gears 2350, 2352, which are positioned at the first end of the magnet2308, and are radially arranged around the central axis 2310 of themagnet 2308 adjacent to gears 2346, 2348, respectively. The gears 2350,2352 may have a height greater than the height of the gears 2346, 2348such that the gears 2350, 2352 extend outwardly past the gears 2346,2348 along the direction of the central axis 2310. The gears 2350, 2352of the second grouping may have the same, or about the same number ofteeth as the gears 2346, 2348 of the first grouping, for example tenteeth. Likewise, the second grouping may comprise a number of gearscorresponding to the number of gears in the first grouping, for examplethe second grouping may comprise the same number of gears as the firstgrouping.

The gears 2350, 2352 of the second grouping may act as planetary gearsand can engage with a first sun gear 2354 positioned at a first end ofthe magnet 2308 such that the central axis of the sun gear 2354 isaligned with the central axis 2310 of the rotatable element, for examplethe magnet 2308, of the driving member 2306. The sun gear 2354 comprisesa greater number of teeth than each of the gears 2350, 2352 so as toprovide a gear reduction and amplify the torque generated by therotatable element of the driving member 2306. For example, the sun gear2354 may comprise sixteen teeth. In some embodiments the sun gear maycomprise from fifteen to thirty teeth, from thirty to fifty teeth, fromfifty to one hundred teeth, or more than one hundred teeth. The sun gear2354 additionally engages with a first intermediate gear 2356 thatcomprises a greater number of teeth than the sun gear 2354 so as soprovide a gear reduction and amplify the input torque from the sun gear2354. The first intermediate gear 2356 may comprise a number of teethcorresponding to the number of teeth of the sun gear 2352, for exampletwice as many teeth, four times as many teeth, eight times as manyteeth, or more. In some embodiments the first intermediate gear maycomprise thirty-two teeth.

The first intermediate gear 2354 can be fixedly attached to the secondintermediate gear 2356 such that the central axes of the gears 2354,2356 are substantially aligned. One rotation of the first intermediategear 2354 will thereby result in one rotation of the second intermediategear 2356. The second intermediate gear 2356 comprises fewer teeth thanthe first intermediate gear 2354, for example half as many teeth, onequarter as many teeth, one eighth as many teeth or fewer. In someembodiments the second intermediate gear 2356 may comprise sixteenteeth. The second intermediate gear 2356 engages with the teeth of thefirst driver 2312 and provides for a gear reduction between the rotationof the rotatable element of the driving member 2306 and the first driver2312 as described above. As described above, the first gear module 2344therefore allows the relatively small torque generated by the drivingmember 2306 to be converted into a relatively high torque at the firstdriver 2312, the rotation of which thereby causes the first rod 2320 tomove along a first longitudinal axis 2336 (FIG. 23A) in a firstlongitudinal direction 2338.

The spinal adjustment implant 2300 may additionally comprise a secondgear module 2358 which is substantially similar to the first gear module2344 and is positioned at the second end of the rotatable element of thedriving member 2306. The second gear module 2358 can be placed betweendriving member 2306 and the second driver 2316 and may function in asubstantially identical manner as the first gear module 2344 asdescribed above. Additionally, in some embodiments the first and secondgroupings of gears of the second gears module may be attached or engagedwith the corresponding gears of the first and second grouping of thefirst gear module 2344. For example, the corresponding gears of thefirst and second groupings of the first and second gears modules mayshare corresponding axles. The sun gears of the first and second gearmodules may not be attached or engaged with one another and the sun gear2354 of the first gear module may rotate independently from the sun gearof the second gear module 2358.

Furthermore, the threaded portions of the first and second rods 2324,2328 and the threaded portions of the first and second drivers 2312,2316 are configured such that rotation of the rotatable element of thedriving member 2306 causes a corresponding rotation of the first andsecond drivers 2312, 2316 which thereby causes the first rod 2324 tomove in a first axial direction 2328 and the second rod 2328 to move ina second axial direction 2342.

As illustrated in FIG. 23A, the first and second gear modules 2344, 2358may be positioned within a first gear module housing 2360 and a secondgear module housing 2362, respectively. The gear module housings 2360,2362 can be attached to, and/or integrally formed with the housing 2302and positioned at the first and second ends thereof. The gear modulehousings 2360, 2362 may include cavities configured to maintain the gearmodules or modules therein. The cavities may include elements configuredto maintain certain elements of the assembly within the housings 2360,2362, for example, protrusions, grooves, or abutments. The housings2360, 2362 may be made from materials which are biocompatible and whichmay allow for relatively small wall thicknesses while maintaining thestructural integrity of the housings 2360, 2362 when in use. Forexample, the housings 2360, 2362 may comprise the same or similarmaterials as the housing 2302.

The spinal adjustment implant 2300 may further comprise a retainer 2364which is configured to receive the threaded portions 2322, 2330 of thefirst and second rods 2320, 2328. The retainer can take the form of, forexample, a hollow tube, with the threaded portions 2322, 2330 of therods disposed therein. The retainer 2364 can be secured to a portion ofthe skeletal system, for example a third vertebra, preferably positionedbetween the first and second vertebra. The retainer 2364 can be securedto the third vertebra directly, by a third extension member 2366, and/orin a manner similar to the manner in which the first rod 2320 is securedto the first vertebra as described above. The third extension member2366 may be coupled to the third vertebra directly, via one or more of:a pedicle screw; hook; wire; or other attachment system. The retainer2364 can be attached to, and/or integrally formed with the gear modulehousings 2360, 2362 at the respective ends of the retainer 2364. In thismanner the retainer 2364, which is secured to a portion of the skeletalsystem, may provide support for, and secure, the housing 2302 via thegear module housings 2360, 2362, within the body of the patient. Acentral axis of the retainer 2364 may be substantially parallel to acentral axis of the driving member driving member 2306, with an offsettherefrom. In some embodiments the offset between the central axis ofthe retainer 2364 and the central axis of the housing 2302 and/ordriving member 2306 may be about 12 mm. In some embodiments the offsetmay be from about 4 to about 16 mm, greater than 16 mm, or greater than32 mm or greater.

FIGS. 24A-24D generally illustrate an embodiment wherein a motor ormagnet, etc. drives a worm that engages and turns a worm gear which maybe rotationally coupled (e.g., in serial) with a pinion that drives arack. FIGS. 24A-D illustrate another embodiment of the spinal adjustmentimplant 2400. The spinal adjustment implant 2400 includes a drive member2402, a first rod 2404, a second rod 2406, a first securement portion2408, a second securement portion 2410, and a third securement portion2412.

As illustrated in FIG. 24A-24B, the driving member can include a firstend that is attached to a worm screw 2416 of a worm drive 2414. As thedrive member 2402 rotates, the worm screw 2416 of the worm drive 2414 isrotated. The worm screw 2416 is configured to engage the worm wheel 2418of the worm drive 2414 and translates the rotational energy of the drivemember 2402 and worm screw 2416 in a first direction to a rotation in asecond direction. In some embodiments, the driving member can be amagnet. The magnet may be 9 mm in diameter and 25 mm long. The drivemember 2402 and the worm drive 2414 can be covered in a flexiblemembrane or below covering assembly that can be configured to protectthe teeth of the worm drive 2414 from body materials. In someembodiments, this housing 2420 can be 10 mm in diameter, 38 mm long, and10 mm in offset.

In some embodiments, the first rod 2404 and the second rod 2406 caninclude a tooth portion that is configured to engage the teeth of theworm wheel 2418. The first rod 2404 and second rod 2406 can include anexternal housing 2422 that can secure the position of the first rod 2404and second rod 2406 about the worm wheel 2418. As illustrated in FIG.24C, one end of the first rod 2404 is located above one end of thesecond rod 2406. In some embodiments, the first rod 2404 has a firstengagement portion 2424 that includes a plurality of teeth that isconfigured to engage the teeth of the worm wheel 2418 above the secondrod 2406. In some embodiments, the second rod 2406 has a secondengagement portion 2426 that includes a plurality of teeth that isconfigured to engage the teeth of the worm wheel 2418 below the firstrod 2404.

FIG. 24C illustrates the movement of the first rod 2404 and the secondrod 2406 as the worm wheel 2418 of the worm drive 2414 is rotated. Asshown by the arrows in FIG. 24C, as the worm wheel 2418 rotates in afirst direction, it causes the first engagement portion 2424 of thefirst rod 2404 and the second engagement portion 2426 of the second rod2406 to engage with the teeth and to move past each other. As the firstrod 2404 and the second rod 2406 move past each other, the first rod2404 pivots downward near the engagement portion to cause the oppositeend of the first rod 2404 to tilt upward. Similarly, as the worm wheel2418 engages the second engagement portion 2426 of the second rod 2406,the second rod 2406 pivots downward near the engagement portion to causethe opposite end of the second rod 2406 to tilt upward. In someembodiments, this compression near the worm wheel 2418 can occursimultaneously in both the first rod 2404 and the second rod 2406 asshown. The compression does not need to be purely linear as there is arotational degree of freedom. In some embodiments, the first rod 2404and the second rod 2406 can be bent past each of the respectiveengagement portions.

FIG. 24D illustrates a cross sectional view of the spinal adjustmentimplant 2400 as it is implanted into a plurality of vertebra of thespinal system. The first rod 2404 can be secured to a first vertebra2428 of the spinal system using a first securement portion 2408. In someembodiments, the first securement portion 2408 can be a screw. In someembodiments, the second rod 2406 can be secured to a second vertebra2430 of the spinal system using a second securement portion 2410.Similarly, in some embodiments, the second securement portion 2410 canbe a screw. In some embodiments, a third securement portion 2412adjacent to the second engagement portion 2426 of the second rod 2406can be secured to a middle vertebra 2432 of the spinal system. In someembodiments, the middle vertebra 2432 can be located between the firstvertebra 2428 and the second vertebra 2430.

As illustrated in FIG. 24D, the third securement portion 2412 can be thepoint about which compression of the first vertebra 2428 and secondvertebra 2430 occur. As seen, as the worm wheel 2418 rotates, the firstengagement portion 2424 of the first rod 2404 can move past the secondengagement portion 2426 of the second rod 2406. The ends of the firstrod 2404 and second rod 2406 where the respective engagement portionsare located bend downward, such that either ends of the first rod 2404and second rod 2406 bend upwards. This can create a curve in the spinalsystem about the middle vertebra 2432.

FIGS. 25A-25E generally illustrate an embodiment including a Torsendifferential which may allow a single motor or magnet output (rotation)to drive two sides of an implant at the same rate, or at different ratesfrom each other. For example, different displacement rates or differentangulation change rates. FIGS. 25A-25E illustrate a spinal adjustmentimplant 2500 for implantation along the spinal system of a subject. Thespinal adjustment implant 2500 is similar to the implant 700 of FIG. 9as it includes a first pivotable interface and a second pivotableinterface that may allow a potentially greater increase in the lordoticCobb angle during compression than that permitted by spinal adjustmentimplants such as the spinal adjustment implant 500 of FIGS. 1-3C. Asdiscussed above for related implants, the spinal implant 2500 isconfigured to be used in place of traditional rods, which are used tomain posterior decompression and stabilize during fusion. Someembodiments of the spinal implant 2500 are compatible with interbodyspacers placed between the vertebrae being treated.

The spinal implant 2500 comprises a housing 2502 having a first end 2504and a second end 2506. The housing 2502 can include a plurality ofportions that extend between the first end 2504 of the housing 2502 andthe second end 2506 of the housing 2502. In some embodiments, thehousing 2502 can include a first extendible portion 2508, a planethousing 2512, a second extendible portion 2510, and a magnet housing2514.

The planet housing 2512 can include openings at both ends and a cavity2513 there through. As will be discussed in more detail below, theplanet housing 2512 can be configured to house a plurality of gears thatcan translate rotational motion into a longitudinal extension orretraction through the housing 2502.

In some embodiments, the planet housing 2512 is positionedlongitudinally between the first extendible portion 2508 and the secondextendible portion 2510. The first extendible portion 2508 is located atthe first end 2504 of the housing 2502 and the second extendible portion2510 is located at the second end 2506 of the housing 2502. The firstextendible portion 2508 and the second extendible portion 2510 can bothinclude a first cavity 2509 and a second cavity 2511 respectively thatcan house a screw. In some embodiments, the first extendible portion2508 and the second extendible portion 2510 can include a projectionportion 2516, 2518 that extends perpendicularly from the surface of thefirst extendible portion 2508 and second extendible portion 2510respectively. A rod 2517 can be configured to extend from the projection2516 in a first direction and a rod 2519 can be configured to extendfrom the projection 2518 in a second direction such that the rod 2517and rod 2519 extend in opposite directions away from each other. As willbe discussed in more detail below, in some embodiments, the first cavity2509 and the second cavity 2511 can include an inner thread that caneach threadingly engage their respective screws such that rotation ofeach of the screws can cause the first extendible portion 2508 and thesecond extendible portion 2510 to extend or retract from the planethousing 2512.

The magnet housing 2514 can be located adjacent to the planet housing2512 such that the magnet housing 2514 and the planet housing 2512 runparallel to one another. The magnet housing 2514 can include a cavity2514 which extends between the first end 2504 and the second end 2506.The cavity 2514 may have a variable inner diameter along its length ormay have a generally constant inner diameter. The inner wall of themagnet housing 2514 may have circumferential grooves or abutments (notillustrated) that axially maintain certain elements of the assembly. Adriving member 2520 can be rotatably disposed within the cavity 2515.The driving member 2520 may comprise any non-invasively rotatableelement such as those described in relation to FIGS. 20-23 . In someembodiments, the driving member 2520 can be a magnet. In someembodiments, the magnet may be 9.5 mm in diameter and 41 mm long. Ofcourse it will be understood that other dimensions may be used. In someembodiments, the planet housing 2512 and the magnet housing 2514 caninclude a side opening near the second end of the planet housing 2512and magnet housing 2514 that provides an interior connection between theplanet housing 2512 and the magnet housing 2514. As will be discussed inmore detail below, the interior connection can house a gear system thattranslates rotational movement of the driving member 2520 intolongitudinal translation (e.g., extension or retraction) of the firstextendible portion 2508 and the second extendible portion 2510.

FIG. 2C illustrates an enlarged view of the second end 2506 of thespinal adjustment implant 2500 with the housing 2502 removed. In someembodiments the housing 2502 can include a driving member 2520, a wormdrive 2530, a miter gear mesh 2540, a first screw 2524, a second screw2522, a Torsen differential 2524 that is housed in a planet carrier2552.

In some embodiments, the driving member 2520 can be disposed about a rod2531 that extend from the second end 2506 and is rotationally coupled toa worm drive 2530. The worm drive 2530 can include a worm screw 2532 anda worm wheel 2534. In some embodiments, the worm gear reduction may be20:1. As the driving member 2520 is rotated, the attached rod 2531rotates the worm drive 2530 which causes the worm wheel 2534 to turn.

In some embodiments, the worm drive 2530 may engage a miter gear mesh2540 which can translate the rotational energy of the worm drive 2530into longitudinal movement along the length of the housing 2502. A typeof bevel gear, miter gears are useful for transmitting rotational motionat a 90 degree angle. In some embodiments, the miter gear mesh 2540 cantranslate rotational motion at a 90 degree angle with a 1.3:1 ratio. Insome embodiments, the miter gear mesh 2540 can be replaced with any typeof gear system that can translate rotational motion at an angle. Themiter gear mesh 2540 can include a first gear 2542 and a second gear2544. In some embodiments, the first gear 2542 is attached to the wormwheel 2534, such that rotation of the worm wheel 2534 causes rotation ofthe first gear 2542. The first gear 2542 can have a plurality of teeththat can engage with the teeth of the second gear 2544. The second gear2544 can be disposed about a rod 2523 such that rotation of the secondgear 2544 causes rotation of the rod 2523 in the same direction.

In some embodiments, the second gear 2544 of the miter gear mesh 2540can be attached to a rod 2554 that engages with a Torsen differential2550 that is located within a planetary carrier 2552. A Torsendifferential, and in similar gear systems, serves to provide amechanical self-locking center differential which regulates the powerbetween the front and rear axles according to demand. A Torsendifferential operates on the basis of torque sending and responds tovarying rotational forces between the input and output shafts. This canenable variable distribution of the driving torque between the axles. Ona Torsen differential, the plurality of output gears are interconnectedby worm gears. This can limit high differential rotational speeds, butstill balance the speeds when cornering. As will be discussed in moredetail below, the Torsen differential 2550 can provide a different rateof rotation of attached members.

FIG. 25D illustrates an enlarged view of the Torsen differential 2550without the planetary carrier 2552. As can be seen, the Torsendifferential 2550 can engage with the rod 2554 at a second end 2506 anda portion of the first screw 2524 at a first end 2504. In someembodiments, as illustrated in FIG. 25B-25D, rotation of the rod 2554 bymiter gear mesh 2540 can cause the Torsen differential 2550 to translatethe rotational energy to the first screw 2524.

As discussed above, the spinal adjustment implant 2500 can be sued tonon-invasively maintaining or changing the magnitude of compressionbetween two vertebrae following fusion surgery (post-operatively) and/ornon-invasively changing the magnitude of lordosis. As well, because thespinal adjustment implant 2500 includes a plurality of pivotalinterfaces, the spinal adjustment implant 2500 can provide for apotentially greater increase in the lordotic Cobb angle duringcompression. This can be done by first rotating the driving member 2520which causes rotation of the worm screw 2532 of the worm drive 2530. Theworm screw 2532 engages with the worm wheel 2534 of the worm drive 2530and rotates the attached first gear 2542 of the miter gear mesh 2540. Asdiscussed above, the first gear 2542 of the miter gear mesh 2540 engageswith the second gear 2544 of the miter gear mesh 2540 to translate therotational energy at an angle. The rotation of the second gear 2544rotates the attached rod 2523 and engages the Torsen differential 2550.As discussed above, the Torsen differential 2550 can engage with aportion of the first screw 2524 to rotate the first screw 2524. As well,the rod 2523 is attached to the second screw 2522 and rotates the screw.In some embodiments, the Torsen differential 2550 can provide the sameor a different rate of rotation of the first screw 2524 and the secondscrew 2522. In some embodiments, this can provide for differentdisplacement rates between the first screw 2524 and the second screw2522. In some embodiments, this can produce the same or differentangulation change rate between vertebrae that are attached to the spinaladjustment implant 2500.

As discussed above, in some embodiments, the first extendible portion2508 and the second extendible portion 2510 further include a firstcavity 2509 and second cavity 2511 respectively. Each of the firstcavity 2509 and second cavity 2511 can further include a threadedinterior that can be configured to movably engage the first screw 2524and second screw 2522 respectively. In some embodiments, the rotation ina first rotational direction of the driving member 2520 causes both thefirst screw 2524 and the second screw 2544 to move into the first cavity2509 and second cavity 2511 respectively. This can cause the rod 2517attached to the first extendible portion 2508 and the rod 2519 of thesecond extendible portion 2510 to move towards each other and reduce thereach of the rod 2517 and rod 2519. This motion is capable of generatinga force on the spine at the points of attachment of the spinaladjustment implant 2500 and increasing the compressive force(s) betweenthe vertebrae.

Similarly, in some embodiments, the rotation in a second rotationaldirection of the driving member 2520 causes both the first screw 2524and the second screw 2544 to extend out of the first cavity 2509 andsecond cavity 2511 respectively. The rotation in a second rotationaldirection can cause the first extendible portion 2508 and the secondextendible portion 2510 to move in opposite directions along the sameaxis. This can cause the rod 2517 attached to the first extendibleportion 2508 and the rod 2519 of the second extendible portion 2510 tomove away from each other and increase the reach of the rod 2517 and rod2519. This motion is capable of generating a force on the spine at thepoints of attachment of the spinal adjustment implant 2500 anddecreasing the compressive force(s) between the vertebrae.

In some embodiments, the inner threading of the first cavity 2509 andsecond cavity 2511 can cause the first screw 2524 and second screw 2544to rotate to move the attached first extendible portion 2508 and secondextendible portion 2510 to move in the same direction along the sameaxis. For example, the first extendible portion 2508 can move in a firstdirection along the axis, wherein the first screw 2524 extends out ofthe first cavity 2509 and the second extendible portion 2510 can move ina first direction as well along the axis, wherein the second screw 2544retracts into the second cavity 2511. The attached rod 2517 and rod 2519thereby move in the first direction. In some embodiments, the distancebetween the rod 2517 and rod 2519 can maintain their distance, reducetheir distance, or increase in distance. The aforementioned embodimentcould apply in the reverse as well—wherein the first extendible portion2508 and second extendible portion 2510 move in a second direction alongthe axis.

FIGS. 25A and 25E illustrate the spinal adjustment implant 2500 securedto a plurality of vertebra. The spinal adjustment implant 2500 can besecured to a plurality of vertebrae that are secured using a pluralityof rods. As illustrated in FIG. 25E, the spinal adjustment implant 2500includes a first rod 2561 located near the first end 2504 of the housing2502. The first rod 2561 can be configured to couple to a first portionof the spinal system. The first portion of the spinal system may be afirst vertebra 2571. In some embodiments, the spinal adjustment implant2500 includes a second rod 2563 located near the second end 2506 of thehousing 2502. The second rod 2563 can be configured to couple to asecond portion of the spinal system. The second portion of the spinalsystem may be a second vertebra 2573. In some embodiments, the spinaladjustment implant 2500 includes a middle rod 2562 located between thefirst end 2504 and the second end 2506 of the housing 2502. The middlerod 2562 can be configured to couple to a third portion of the spinalsystem. The third portion of the spinal system may be a third vertebra2572 located between the first vertebra 2571 and the second vertebra2573. As indicated, a first angle of rotation is in a clockwisedirection while a second angle of rotation is in a counter-clockwisedirection. As noted in FIG. 25A, the Torsen differential can cause therotation about the first and second angles of rotation to occur at thesame or different rates.

In some embodiments, the first rod 2561 and second rod 2563 can serve asa plurality of pivotable interfaces that can allow a potentially greaterincrease in the lordotic Cobb angle during compress. As is illustratedin FIG. 25E, the first rod 2561 and second rod 2563 allow the securedfirst vertebra 2571 and the second vertebra 2573 to pivot about themiddle rod 2563 that is secured to the third vertebra 2572. Thedirection of the rotation of the rods is illustrated by the curvedarrows illustrated in FIG. 25E. In some embodiments, the first rod 2561and second rod 2563 are non-invasively lockable and nonlockable. In someembodiments, the first and second rods 2561, 2563 are configured to benon-invasively lockable and unlockable as part of the non-invasiveadjustment. In some embodiments, the first and second rods 2561, 2563are configured to be non-invasively lockable and unlockable inconjunction with the rotation of the driving member 2520.

In some embodiments, the first and second rods 2561, 2563 areintermittently locked and unlocked during an adjustment procedure.

In some embodiments, one or more of the pivotable interfaces isconfigured to rotate freely in either direction (e.g., clockwise and/orcounterclockwise). In some embodiments, one or more of the pivotableinterfaces is partially constrained to have free rotation in onedirection but no rotation in the other direction—this may beaccomplished using a free wheel or other one-way clutching. In someembodiments, the rods include two-way locking so that they may lock andunlock automatically by the operation of the spinal adjustment implant.For example, the Eternal Remote Controller (ERC) may be used to lock andunlock a magnetic lock which is capable of reversibly removing therotational freedom of the pivotable interface(s). In some embodimentswhich may be either freely rotating or lockable, there may additionallybe constrained rotation or motion, wherein there are limits, extents, ordetents that limit the total amount of travel of a particular rotationor motion.

FIGS. 26A-26H generally illustrate a motor or magnet that by use of acam is able to intermittently lock or unlock a mechanism, as it isadjusted. In some embodiments, the unlocking may temporarily allow forchange in angulation, which is then locked again, after the changeoccurs. FIGS. 26A-26H illustrate various views of a pivot lock mechanism2600, according to some embodiments. The pivot lock mechanism 2600 maybe used, for example, to lock and unlock the first and second pivotableinterfaces 729, 727 of the spinal adjustment implant 700 shown in FIG. 9. The pivot lock mechanism 2600 includes a motor 2602 operably coupledto a drive shaft 2608. In some embodiments, the motor 2602 comprises amagnet that may be magnetically coupled to one or more other magnets.For example, in some embodiments, the motor 2602 may be magneticallycoupled to the one or more magnets of the magnetic handpiece 178 shownin FIGS. 4 and 5 . In some embodiments, the magnet 2602 comprises acylindrical, radially-poled permanent magnet, although any suitablesize, shape, and polarity is appreciated. The magnet may include a northpole 2618 and a south pole 2620. As shown in FIGS. 26A-26H, the driveshaft 2608 may extend longitudinally from the motor 2602. In someembodiments, the center longitudinal axes of the motor 2602 and thedrive shaft 2608 are aligned. The motor 2602 and the drive shaft 2608may be operably coupled such that the drive shaft 2608 rotates when themotor 2602 rotates. In some embodiments, the drive shaft 2608 and themotor 2602 rotate at the same angular velocity and/or at differentangular velocities. For example, in some embodiments, the motor 2602rotates at one, two, three, or more discreet angular velocities, and/orat any angular velocity between a minimum and maximum value. However, itshould be appreciated that the motor 2602 and the drive shaft 2608 mayrotate at any suitable angular velocity. In some embodiments, the motor2602 can rotate in either direction (e.g., clockwise and/orcounterclockwise).

The pivot lock mechanism 2600 further includes a rod 2616, a pivotmember 2614, and a pin 2615. In some embodiments, a first end of the rod2616 may be attached to, for example, a pedicle screw, and a second endof the rod 2616 may be attached to the pivot member 2614. In someembodiments, the rod 2616 can be any of the rods disclosed herein, suchas the rod shown in FIG. 48 . The pin 2615 may couple the pivot member2614 to a pivot slide 2612. In some embodiments, the pivot slide 2612includes a slot 2621 configured to accommodate first and second pivotlocks 2604 a, 2604 b. The first and second pivot locks 2604 a, 2604 bmay be constrained to vertical motion and may be independently springloaded downward with corresponding first and second elastic members 2606a, 2606 b, respectively. In some embodiments, the first and secondelastic members 2606 a, 2606 b comprise springs, such as, for example,compression springs. As the pivot member 2614 rotates, the pivot slide2612 is configured to translate horizontally back and forth. Forexample, in some embodiments, the pivot slide 2612 may be able tocyclically translate in opposing first and second directions. In someembodiments, the horizontal translation of the pivot slide 2612 isperpendicular relative to the vertical motion of the first and secondpivot locks 2604 a, 2604 b. Translation of the pivot slide 2612 maycause the rod 2616 to adjust the positioning of one or more pediclescrews and/or the positioning of one or more other rods.

As shown in FIGS. 26D and 26E, the slot 2621 has two ramps 2622, 2624spaced opposite of each other. The bottom surface of the slot 2621 thatextends between the two ramps 2622, 2624 may be flat or any othersuitably shaped surface. The first and second pivot locks 2604 a, 2604 bmay be configured to settle into ramps 2624, 2622, respectively,regardless of the angle of the rod 2616. In some embodiments, the rod2616 is unable to force the pivot slide 2612 to move when the first andsecond pivot locks 2604 a, 2604 b are in place. FIGS. 26D and 26Eillustrate two exemplary views showing the first and second pivot locks2604 a, 2604 b locked in place.

The pivot lock mechanism 2600 also includes a cam 2610 operably coupledto the drive shaft 2608. The cam 2610 alternately unlocks and locks thepivot member 2614 by engaging the first and second pivot locks 2604 a,2604 b. Rotation of the cam 2610 may alternately unlock and lock thepivot member 2614 as it is rotated. For example, in some embodiments,unlocking the pivot lock mechanism 2600 may temporarily allow for achange in angulation of the rod 2616, after which the pivot member 2614may be locked.

For example, as shown in FIG. 26G, the cam 2610 may intermittentlyunlock the pivot member 2614 by lifting the first and/or second pivotlocks 2604 a, 2604 b upward by overcoming the downward force exerted bythe first and/or second elastic members 2606 a, 2606 b, respectively. Insome embodiments, when the pivot member 2614 is unlocked, a rotation ofthe pivot member 2614 in the range of about 1 degree to about 45 degreesmay cause a translation of the pivot slide 2612 in the range of about0.01 mm to about 0.8 mm, although any suitable range for theserespective movements are appreciated. For example, in some embodiments,a 10 degree rotation of the pivot member 2614 may cause a 0.5 mmtranslation in the pivot slide 2612. As shown in FIG. 26F, the cam 2610may intermittently lock the pivot member 2614 when the first and/orsecond pivot locks 2604 a, 2604 b settle back into the slot 2621 afterthe cam 2610 disengages the first and/or second pivot locks 2604 a, 2604b. In some embodiments, the cam 2610 may lift the first and/or secondpivot locks 2604 a, 2604 b for a prescribed duration, the duration ofwhich may be controlled by the cam shape and/or gearing. As a result, asthe cam 2610 is rotated by the drive shaft 2608, the first and secondpivot locks 2604 a, 2604 b may move in opposing first and secondvertical directions. Further, in some embodiments, the cam 2610 mayrotate in either direction (e.g., clockwise and/or counterclockwise),and in other embodiments, the cam 2610 may rotate in only one direction(e.g., only clockwise or counterclockwise). With reference to FIG. 26H,various dimensions of the pivot lock mechanism 2600 are shown. However,it should be understood that while certain dimensions are shown in FIG.26H, other suitable dimensions are also appreciated.

FIGS. 27-30 illustrate various types of spinal implant adjustmentstructures 2700, according to some embodiments. The adjustmentstructures 2700 may be used, for example, to adjust one or more rods ofthe spinal implants shown in FIGS. 1-12 . For example, the adjustmentstructures 2700 may be functionally similar to driving members 514 and814 shown in FIGS. 3A and 12 . Similar to driving members 514 and 814,the adjustment structures 2700 may be configured to engage first andsecond threaded drivers to cause pistoning of one or more correspondingrods. For example, with reference to implant structures illustrated inFIG. 3A, in some embodiments the adjustment structures 2700 may be usedin lieu of driving member 514 to rotate the first and second threadeddrives 528, 542 to cause the first and second rods 558, 588 to move intoor out of the cavity 508 of the housing 502, thereby causing thelongitudinal distance L between points A and B to decrease or increase.Of course, it should be appreciated that any of the adjustmentstructures 2700 shown in FIGS. 27-30 may be used as a driving member inany of the spinal implant embodiments described herein.

Each of the adjustment structures 2700 shown in FIGS. 27-30 may beactivated in a different way to rotate one or more threaded drivers andcause pistoning of one or more corresponding implant rods. For example,FIG. 27 illustrates hydraulic activation, FIG. 28 illustrates magneticfluid pump activation, and FIGS. 29 and 30 illustrate composite fluidcoil spring activation. Similar to the driving members described above,the adjustment structures 2700 are configured to rotate one or morethreaded drivers by delivering energy to them when activated.

As shown in FIG. 27 , the hydraulic activated adjustment structure 2700may be fluidically connected to a minimally invasive hydraulic system2710. The hydraulic system 2710 may include a fluid pump 2702, first andsecond tubing segments 2703, 2710, first and second hypo needles 2704,2709, and a fluid reservoir 2711. The adjustment structure 2700 mayinclude first and second cannulated rods 2714, 2715 into which the firstand second hypo needs 2704, 2709 may be inserted after being insertedthrough the skin 2720 and subdermal tissue. In some embodiments, thefirst and second cannulated rods 2714, 2715 have one or more accesspoints (e.g., access points 2712 and 2713) positioned along their lengthso that the first and second hypo needles 2704, 2709 may access thefirst and second cannulas 2705, 2708 of the first and second cannulatedrods 2714, 2715. Each access points may be, for example, a hole coveredby septum such as a rubber stopper which prevents surrounding bodilyfluid from entering the adjustment structure 2700.

As shown in FIG. 27 , the adjustment structure 2700 may include achamber 2706 which houses an impeller 2707. As fluid is pumped throughthe chamber 2706, the impeller rotates. In some embodiments, therotation of the impeller drives the first and second cannulated rods2714, 2715, and in some embodiments, the rotation of the impeller drivesfirst and second threaded drivers (not shown), thereby causing pistoningof the first and second cannulated rods 2714, 2715. Further, as shown inFIG. 27 , in some embodiments, the chamber 2706 may be tapered into anozzle at one end to increase the velocity of the fluid flowing past theimpeller 2707. In some embodiments, the first and second cannulas 2705,2708 are the same or different sizes depending on the flow rate to beachieved across the impeller 2707. In some embodiments, fluid ispost-operatively delivered to the adjustment structure 2700 via a simpleprocedure such as an injection. The injected fluid may increase ordecrease the length of the implant by turning the impeller 2707 asdescribed above. In some embodiments, the fluid pumped by the hydraulicsystem may be saline, although any suitable fluid is appreciated. Forexample, in other embodiments, a biphasic fluid may be used so that itschange in characteristics (e.g., volume) can be harnessed. For example,SF₆ (Sulfur Hexafluoride) or C₃F₈ (Octafluoropropane) may be used. Inaddition, in some embodiments, a ratchet mechanism may be used in tandemto maintain device length change as the impeller rotates.

FIG. 28 generally illustrates an implant comprising amagnetically-driven impeller to drive fluid pressure and/or flow changesto cause pistoning adjustment of a rod which is dynamically sealedwithin a cavity of a housing. The adjustment structure 2700 illustratedin FIG. 28 is similar to that shown in FIG. 27 except that the impeller2707 in FIG. 28 is driven by a magnet rotor 2717 rather than fluid flowalone. In some embodiments, the magnetically-driven impeller 2707 drivesfluid pressure and/or flow changes to cause pistoning adjustment of oneor more rods (e.g., first and second cannulated rods 2714, 2715). Insome embodiments, the one or more rods may be sealed within a cavity ofa housing of the spinal implant, and in some embodiments, the one ormore rods may be dynamically sealed within a cavity of a housing of thespinal implant. Although not shown, a hydraulic system may be connectedto the adjustment structure 2700. In some embodiments, themagnetically-driven impeller 2707 moves fluid from a first reservoir toa second reservoir of the hydraulic system.

FIG. 29 generally illustrates an implant having a support structure(e.g., a skeleton) that has an internal pressurized chamber or series ofchambers that cooperatively maintain axial stiffness. By selectivelyremoving fluid from one or more chamber (some or all of the fluid), thepressure may be controllably decreased, thereby lessening the totalaxial compression, and allowing the controlled shortening of theimplant. Each chamber may be configured to be permanently punctured,wherein all of its fluid is removed, or may have a resealable skin,wherein a controlled amount of fluid may be removed, or even replaced.FIG. 29 illustrates an adjustment structure 2700 comprising a compositefluid coil spring assembly 2902. In some embodiments, the assembly 2902includes a support structure 2904 (also referred to as a skeleton) andan extension spring 2906. In some embodiments, the extension spring 2906supplies a compressive force (i.e., potential energy) to the supportstructure 2904. The support structure 2904 may include one or more fluidfilled chambers 2905 that maintain the axial stiffness of the extensionspring 2906. In some embodiments, the chambers 2905 may be pressurized.By selectively removing fluid from one or more of the chambers 2905(e.g., some or all of the fluid), the pressure in one or more of thechambers 2905 may be controllably decreased, thus lessening the totalaxial compression exerted by the extension spring 2906, and therebyallowing the length of the implant to be controllably shortened. In someembodiments, each chamber may be configured to be permanently punctured,wherein all of its fluid is removed, or may have a resealable skin,wherein a controlled amount of fluid may be removed, or even replaced.By selectively replacing fluid into one or more the chambers 2905, thepressure in one or more of the chambers 2905 may be controllablyincreased, thus increasing the total axial compression exerted by theextension spring 2906, and thereby allowing the length of the implant tobe controllably lengthened. The support structure 2904 thereby controlsthe amount of collapse and/or expansion of the extension spring 2906.The one or more chambers 2905 store compressive energy by resisting thecompressive force exerted by the extension spring 2906. By selectivelyremoving fluid from one or more of the chambers 2905 (e.g., some or allof the fluid), the extension spring 2906 becomes activated (i.e., it isallowed to compress). In some embodiments, a needle 2908 and a syringe2910 may be used to remove fluid from one or more of the chambers 2905,although any suitable fluid removal method and/or apparatus isappreciated. In some embodiments, saline may be used to fill thechambers 2905, although any suitable fluid is appreciated.

FIG. 30 generally illustrates an implant that is similar to theembodiment in FIG. 29 , but the “skeleton” is replaced by a compressionspring. Fluid may be removed (as described in relation to FIG. 29 ) or,as shown in FIG. 30 , a magnetic release valve may be operatednon-invasively (with an external magnetic field), to open an orifice toallow fluid to escape (pressure to decrease). FIG. 30 illustrates acomposite fluid coil spring assembly 3002 that is similar to the springassembly 2902 shown in FIG. 29 , but the support structure 2904 ofspring assembly 2902 is replaced by a compression spring 3004. Fluid maybe removed or replaced as described above in relation to FIG. 29 , or,as shown in FIG. 30 , a magnetic release valve 3006 may be operatednon-invasively (e.g., with an external magnetic field), to open anorifice to allow fluid to escape into a fluid reservoir 3008 and allowthe pressure to decrease in the compression spring 3004, therebyallowing the length of the implant to be controllably shortened. In someembodiments, fluid may be replaced in the compression spring 3004,thereby allowing the length of the implant to be controllablylengthened. In some embodiments, the compression spring 3004 isinstalled in tension. The compression spring 3004 may store fluid in oneor more pressurized compartments. In some embodiments, one or more ofthe compartments may be incrementally drained via the magnetic releasevalve 3006. By selectively removing fluid from one or more of thechambers 2905 (e.g., some or all of the fluid), the compression spring3006 becomes activated (i.e., it is allowed to compress).

FIGS. 31A-31C illustrate different types of springs 3100 that may beincorporated, for example into the embodiment of FIG. 30 , to vary theapplication of force as conditions are varied.

FIG. 32 illustrates an implant 3200 having one or more shaped memoryNitinol wires 3202 in tension whose length may be made to change uponapplication of current (for example, non-invasively through inductivecoupling, or via a battery 3204). A change in length of the Nitinolwires 3202 may cause a ratchet 3206 to controllably change the length ofthe implant 3200 by allowing a teethed bar 3208 to freely slide past.The Nitinol wires 3202 may store potential energy which may be activatedremotely via electronics that apply current to the wires. In someembodiments, the application of current to the Nitinol wires causes theNitinol wires to undergo a phase change, such as, for example, changingstate and/or shape. For example, in some embodiments, the Nitinol wires3202 contract when current is run through them, shortening the implant3200. Further, in certain embodiments, one or more of the Nitinol wires3202 may be Nitinol springs. In some embodiments, the ratchet 3206 maybe disengaged with the teethed rod 3208 when current is running throughthe wires 3202.

FIG. 33 illustrates an implant 3300 having a magnetically operatedrotational ratchet 3306 that allows the controlled rotation andcompression of a lead screw 3302. A torsion spring 3304 supplies thepotential energy, such that, when the ratchet is in release mode, thelead screw 3302 is turned until the ratchet locks back down. As shown inFIG. 33 , in some embodiments, the torsion spring 3304 may be apre-wound spiral torsion spring, although any suitable torsion spring isappreciated.

FIGS. 34A-34B generally illustrate a harmonic drive that may be usedtogether with any of the embodiments described herein, to increaseefficiency (decrease losses, e.g., frictional losses). In someembodiments, a harmonic drive, also known as a strain wave gear, may beused. A harmonic drive, for example, the embodiments shown in FIGS. 34Aand 34B, may be used together with any of the embodiments describedherein, to increase efficiency. Using a harmonic drive may decreaselosses, such as, for example, frictional losses. Some advantages ofusing a harmonic drive include, but are not limited to, a possibleextremely large gear reduction (150:1), an efficiency between 60-90%depending on the design, and the ability to have the input/output shaftsgenerally along the same axis. In some embodiments, the gear reductionratio may be 120:1. In some embodiments, the efficiency may be 82%.

FIG. 34B shows a harmonic drive 3400 with a wave generator 3410, flexspline 3412, and circular spline 3416. Some advantages of a strain gearwave include, but are not limited to, lack of backlash, compactness andlightweight, high gear ratios, reconfigurable ratios within a standardhousing, good resolution and excellent repeatability (linearrepresentation) when repositioning inertial loads, high torquecapability, and coaxial input and output shafts. High gear reductionratios may be possible in small volume. For example, a harmonic drivemay produce a ratio from 30:1 up to 320:1 in the same space in whichplanetary gears typically only produce a 10:1 ratio.

The wave generator 3410 is attached to an input shaft (not shown). Theflex spline 3412 is like a shallow cup, where the sides of the flexspline 3412 are very thin but the bottom is thick and rigid. Thisresults in significant flexibility of the walls at the open end due tothe thin wall but rigidity in the closed side, where the closed side maybe tightly secured, for example, to a shaft. Teeth 3414 are positionedradially around the outside of the flex spline 3412. The flex spline3412 fits tightly over the wave generator 3410, so that when the wavegenerator plug is rotated, the flex spline 3412 deforms to the shape ofa rotating ellipse but does not rotate with the wave generator 3410. Theflex spline 3412 may attach to an output shaft (not shown). The outputshaft may have a maximum rating of 30-70 mNm. The circular spline 3416is a rigid circular ring with teeth 3418 on the inside. The flex spline3412 and wave generator 3410 are placed inside the circular spline 3416,meshing the flex spline teeth 3414 and the circular spline teeth 3418.Because the flex spline 3412 has an elliptical shape, its teeth 3414only actually mesh with the circular spline teeth 3418 in two regions onopposite sides of the flex spline 3412 along the major axis of theellipse.

In some embodiments, the wave generator 3410 may be the input rotation.As the wave generator plug rotates the flex spline teeth 3414 that aremeshed with the circular spline teeth 3418 change. The major axis of theflex spline 3412 actually rotates with the wave generator 3410, so thepoints where the teeth mesh revolve around the center point at the samerate as the wave generator 3410. In some embodiments, there are fewerflex spline teeth 3414 than there are circular spline teeth 3418, forexample, two fewer teeth. This means that for every full rotation of thewave generator 3410, the flex spline 3412 would be required to rotate asmall amount, for example, two teeth, backward relative to the circularspline 3416. Thus, the rotation of the wave generator 3410 results in amuch slower rotation of the flex spline 3412 in the opposite direction.The gear reduction ratio may be calculated by:

${{reduction}{ratio}} = \frac{\left( {{{flex}{spline}{teeth}} - {{circular}{spline}{teeth}}} \right)}{{flex}{spline}{teeth}}$

For example, if there are 200 flex spline teeth and 202 circular splineteeth, the reduction ratio is (200-202)/200=−0.01. Thus, the flex splinewould spin at 1/100 the speed of the wave generator plug and in theopposite direction.

FIG. 35 generally illustrates a cycloidal drive that may be usedtogether with any of the embodiments described herein. The cycloidaldrive can allow for high ratios (thus significantly reduced speed,increase precision, increased torque delivery) in a small profile. Thecycloidal disc (gold) is driven by an input shaft (green) having aneccentric bearing (green/white), thus turning the cycloidal disc inrelation to the circumferentially oriented ring pins (whitesemi-circles) which are attached to the chassis. (The green shaft may bedriven by a magnet or motor). The holes in the cycloidal disc drive theoutput disc (purple) via the pins (purple). In some embodiments, acycloidal drive may be used, such as the cycloid drive illustrated inFIGS. 35A and 35B. A cycloidal drive, also known as a cycloidal speedreducer is a mechanism for reducing the speed of an input shaft by acertain ratio. A cycloidal drive allows for high ratios in a smallprofile; thus, resulting in significantly reduced speed, increasedprecision, and increased torque delivery. The reduction ratio of thecycloidal drive may be obtained from:

${{reduction}{ratio}} = \frac{\left( {{{number}{of}{ring}{pins}} - {{number}{of}{cycloidal}{disc}{lobes}}} \right)}{{number}{of}{cycloidal}{disc}{lobes}}$

In some embodiments, the reduction ratio may be up to 119:1 for singlestage and up to 7569:1 for double stage. In some embodiments, theefficiency may approach 93% for single stage and approach 86% for doublestage.

The cycloidal disc 3510 is driven by an input shaft 3512 mountedeccentrically to a bearing 3514, thus turning the cycloidal disc 3510 inrelation to the circumferentially oriented ring pins 3516 that areattached to the chassis. The cycloidal disc 3510 independently rotatesaround the bearing 3514 as it is pushed against the ring gear. The holes3518 in the cycloidal disc 3510 drive the output disc 3520 via the pins3522. In some embodiments, the number of ring pins 3516 is larger thanthe number of lobes 3524 in the cycloidal disc 3510 causing thecycloidal disc 3510 to rotate around the bearing 3514 faster than theinput shaft 3512 is moving it around, giving an overall rotation in thedirection opposing the rotation of the input shaft 3512. In someembodiments, the input shaft 3512 may be driven by a magnet or motor.

FIG. 36 generally illustrates a roller screw drive which may be usedtogether with any of the embodiments described herein. The roller screwdrive may allow for increased precision and torque magnification. Aroller screw drive, such as the embodiment shown in FIG. 36 , may beused together with any of the embodiments described herein. The rollerscrew drive may convert rotational motion to linear motion. The rollerscrew drive may allow for increased precision and torque magnification.In some embodiments, the roller screw drive has 75-90% efficiency.

The screw shaft 3610 has a multi-start V-shaped thread, which provides ahelical raceway for multiple rollers 3612 radially arrayed around thescrew shaft 3610 and encapsulated by a threaded nut 3614. In someembodiments, the thread of the screw shaft 3610 is identical to theinternal thread of the nut 3614. In some embodiments, the thread of thescrew shaft 3610 is opposite to the internal thread of the nut 3614.

A spur gear, such as the embodiment shown in FIG. 37 , may be usedtogether with any of the embodiments described herein. In someembodiments, a spur gear may be used as a differential. The advantagesof using a spur gear may include, but are not limited to, allowing oneside to keep advancing even if the other side is stalled, increasingefficiency, being less complex and flexible, and being able to bedesigned to fit around a central screw.

A Torsen-type (also commonly known as a worm gear), such as theembodiment shown in FIG. 38 , may be used together with any of theembodiments described herein. In some embodiments, a worm gear may beused as a differential. The advantages to using a worm gear differentialmay include, but are not limited to, allowing one side to keep advancingeven if the other side has stalled, limiting or eliminating the abilityto back-drive the system.

A differential screw, such as the embodiment shown in FIG. 39 , may beused together with any of the embodiments described herein. A singlescrew 3910 has a first threaded portion 3911 having a first pitch A anda second threaded portion 3912 having a second pitch B. Both firstthreaded portion 3911 and second threaded portion 3912 have the threadsin the same direction as each other. The screw 3910 may have a drivingmember (not shown) directly attached to the screw 3910 or attached tothe screw 3910 via gearing, etc. The first housing portion 3921 may beattached to a first vertebra (not shown) and the second housing portion3922 may be attached to a second vertebra (not shown). As the screw 3910is turned (non-invasively) in a first rotational direction, the firsthousing portion 3921 moves in a first longitudinal direction in relationto the screw 3910 and the second housing portion 3921 moves in a firstlongitudinal direction in relation to the screw 3910. However, becausethe second housing portion 3922 and the second threaded portion 3912have a larger thread pitch B than the thread pitch A of the firsthousing portion 3921 and first threaded portion 3911, the second housingportion 3922 begins to “overtake” the first housing portion 3921 and sothe two housing portions move relatively closer to each other. Thelongitudinal distance that housings move relatively towards each otheris equal to the difference in pitch (B-A) per turn of the screw.

In some embodiments, clutches, such as, for example, those shown inFIGS. 40A-40C, may be required to eliminate the ability for the systemto back-drive. Two types of clutches may help: over running or on/off.Over running clutches only run in one direction, may lack controls, andmay limit and/or eliminate the ability to drive the system in bothdirections. Examples of over running type clutches include: ratchet,needle clutch, free wheel, sprag clutch, spring clutch, face gear.On/off clutches may lock in either direction and need to be controlled(unlocked). Examples of on/off type clutches include: spring clutch withtang and face gears.

In some embodiments, a ball screw mechanism, such as, for example, theembodiment shown in FIG. 41 , may be used together with any of theembodiments described herein, to increase efficiency, and decreaselosses (e.g., frictional losses). Using a ball screw mechanism maydecrease losses, for example, frictional losses. In some embodiments, aball screw mechanism may translate rotational to linear motion. The ballbearings 4114 fit between the screw shaft 4110 and the nut 4112. Theball bearings 4114 may reduce friction and input torque and as a resultimprove efficiency.

FIGS. 42-44 illustrate three different systems of torque split,differential, and/or gear reduction. The features shown in FIGS. 42-44may be used in various combinations, not all of which may be shown inthe figures. The flow charts show some embodiments of systems, where asignal or signals from an external communicator results in compression.In some embodiments, as illustrated by system 4200 in FIG. 42 , anexternal communicator 4210 may generate and transmit a signal 4212 to amotor 4214 in subsystem 4205. The motor output torque 4216 determineshow much, if any, gear reduction 4218 is required. The high torque 4220is split over a differential 4222. In some embodiments, the torque splitratio can vary from 100/0 to 50/50. In some embodiments, the torquesplit ratio is 50/50 so that half the high torque is transmitted to afirst side 4224 and half the high torque is transmitted to a second side4226. In some embodiments, the high torque on the first side 4224 may beconverted from rotary to linear motion 4230 resulting in compression tothe first side 4228. In some embodiments, the high torque on the secondside 4226 may be converted from rotary to linear motion 4232 resultingin compression on the second side 4234. In some embodiments, the rotaryto linear motion conversion mechanisms on the first and second sides4230 and 4232 are the same or substantially similar. In someembodiments, the rotary to linear motion conversion mechanisms on thefirst and second sides 4230 and 4232 are different. In some embodiments,the amounts of compression on the first and second sides 4228 and 4234are the same or substantially similar. In some embodiments, the amountsof compression on the first and second sides 4230 and 4232 aredifferent.

In some embodiments, as illustrated by system 4300 in FIG. 43 , anexternal communicator 4310 may generate and transmit a signal 4312 to amotor 4314. The motor output torque 4316 is split over a differential4318. In some embodiments, the torque split ratio can vary from 100/0 to50/50. In some embodiments, the torque split ratio is 50/50 so that halfthe torque is transmitted to a first side 4320 and half the torque istransmitted to a second side 4322. In some embodiments, the torque onthe first side 4320 is transferred by gear reduction 4326 to increasethe amount of torque, resulting in a high torque 4324. In someembodiments, the torque on the second side 4322 is transferred by gearreduction 4328 to increase the amount of torque, resulting in a hightorque 4330. In some embodiments, the first side gear reduction 4326 isby the same value as the second side gear reduction 4326. In someembodiments, the first and second sides have different gear reductionvalues. In some embodiments, the first and second gear reductions may bedone by similar reduction drives. In some embodiments, the first andsecond gear reductions may be done by the different style reductiondrives. In some embodiments, gear reduction 4326 or 4328 may not benecessary, depending on the value of the torque 4320 or 4322. In someembodiments, the high torque on the first side 4324 may be convertedfrom rotary to linear motion 4334 resulting in compression to the firstside 4332. In some embodiments, the high torque on the second side 4330may be converted from rotary to linear motion 4336 resulting incompression on the second side 4338. In some embodiments, the rotary tolinear motion conversion mechanisms on the first and second sides 4334and 4336 are the same or substantially similar. In some embodiments, therotary to linear motion conversion mechanisms on the first and secondsides 4334 and 4336 are different. In some embodiments, the amounts ofcompression on the first and second sides 4332 and 4338 are the same orsubstantially similar. In some embodiments, the amounts of compressionon the first and second sides 4332 and 4238 are different.

In some embodiments, as illustrated by system 4400 in FIG. 44 , anexternal communicator 4410 may generate and transmit a first signal 4412and a second signal 4414 to a first motor 4416 and a second motor 4418,respectively. In some embodiments, the external communicator maygenerate and transmit at least one signal, such as, for example, one,two, ten, or one hundred signals. In some embodiments, the first signal4412 and the second signal 4414 are the same or substantially similar.In some embodiments, the first and second signals 4412 and 4414 aredifferent. The first motor 4416 is part of a subsystem 4405 and thesecond motor 4418 is part of a subsystem 4415. The motor output torques4420 and 4422 determine how much, if any, gear reduction 4424 and 4426is required. In some embodiments, the first motor output torque 4420 andthe second motor output torque 4422 are the same or substantiallysimilar values. In some embodiments, the first and second motor outputtorques 4420 and 4422 are different values. In some embodiments, theremay be no gear reduction. In some embodiments, the high torque on thefirst side 4428 may be converted from rotary to linear motion 4432resulting in compression to the first side 4336. In some embodiments,the high torque on the second side 4430 may be converted from rotary tolinear motion 4434 resulting in compression on the second side 4438. Insome embodiments, the rotary to linear motion conversion mechanisms onthe first and second sides 4432 and 4434 are the same or substantiallysimilar. In some embodiments, the rotary to linear motion conversionmechanisms on the first and second sides 4432 and 4434 are different. Insome embodiments, the amounts of compression on the first and secondsides 4436 and 4438 are the same or substantially similar. In someembodiments, the amounts of compression on the first and second sides4436 and 4438 are different.

FIGS. 45A-45C generally illustrate various types of a pivot for couplingto pedicle screws, which are able to turn only in a single direction,thus allowing, for example, an increase in lordosis, without a loss.This, the implant will be adjustable only in a first angular direction,and will not allow back adjustment in the opposite angular direction.FIG. 45C illustrates a pivot with a sprag clutch. In some embodiments, aone way locking pivot, such, as for example, the embodiments shown inFIGS. 45A-45C, may be used for coupling to pedicle screws. The pivot maymove in one rotational direction but not the other. In some embodiments,for example, the pivot may be configured to be movable in the rotationaldirection at which lordosis is increased and not be movable in theopposite direction; thus, increasing lordosis without a loss. In someembodiments, the pivot may comprise a freewheel or other one-wayclutching concepts presented herein. Alternatively, one way pivoting maybe provided by a ratchet or other type of commonly known device allowingrotation in one way but not the other. In some embodiments, the pivotmay comprise a sprag clutch, such as for example, the embodiments shownin FIGS. 46A and 46B. Using a pivot may allow an extra degree of freedomfor lordotic compression but may limit how much compression.

FIG. 47 shows an embodiment where the pivot's 4710 rotation iscontrolled by axial movement (e.g., retraction) of an implant. In someembodiments, a pivot may include extension members 4712 that arepartially constrained. For example, they may be constrained in a singlelinear degree of freedom, for example, slidable in a groove or slot 4713or 4714. A first linkage 4715 and a second linkage 4716 are similar tothe boom and stick of a backhoe. The housing 4718 and rod 4720 aresimilar to the backhoe cylinder. Noninvasive shortening of the length ofthe implant (via retraction of rod 4720 into housing 4718) allows slots4713 and 4714 of first linkage 4715 and second linkage 4716,respectively, slide along the housing extension member, which attachesthe housing 4722 to the middle pedicle screw that is connected tovertebra B. The two outer extension members 4712 are rigidly securedrespectively to the first and second linkages 4715 and 4716, and thus,they cause the two outer pedicle screws to rotate and force an increaseof lordosis between vertebra A and vertebra C.

In some embodiments, a torque-limiting brake that is configured to lockand unlock a pivot may be used, such as, for example, the embodimentshown in FIG. 48 . The pivot may allow for changes in angulation, suchas to change an angle of lordosis. At a threshold torque, slippageoccurs at point A, thus unlocking the brake and allowing the pivot 4810to temporarily unlock.

Although this invention has been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. In addition, while a number of variations of the invention havebeen shown and described in detail, other modifications, which arewithin the scope of this invention, will be readily apparent to those ofskill in the art based upon this disclosure. It is also contemplatedthat various combinations or sub-combinations of the specific featuresand aspects of the embodiments may be made and still fall within thescope of the invention. Accordingly, it should be understood thatvarious features and aspects of the disclosed embodiments can becombined with or substituted for one another in order to form varyingmodes of the disclosed invention. Thus, it is intended that the scope ofthe present invention herein disclosed should not be limited by theparticular disclosed embodiments described above, but should bedetermined only by a fair reading of the claims that follow. Therefore,in addition to the many different types of implantable retraction ordistraction devices that are configured to be non-invasively adjusted,implantable non-invasively adjustable non-distraction devices areenvisioned, including, for example, adjustable restriction devices forgastrointestinal disorders such as GERD, obesity, or sphincter laxity(such as in fecal incontinence), or other disorders such as sphincterlaxity in urinary incontinence. These devices, too, may incorporatemagnets to enable the non-invasive adjustment.

Similarly, this method of disclosure, is not to be interpreted asreflecting an intention that any claim require more features than areexpressly recited in that claim. Rather, as the following claimsreflect, inventive aspects lie in a combination of fewer than allfeatures of any single foregoing disclosed embodiment. Thus, the claimsfollowing the Detailed Description are hereby expressly incorporatedinto this Detailed Description, with each claim standing on its own as aseparate embodiment.

What is claimed is:
 1. An adjustable implant, comprising: a first endconfigured to affix the adjustable implant to a first location of asubject; a second end configured to affix the adjustable implant to asecond location of the subject; an actuator configured to be activatedfrom an external location; and a cycloidal drive comprising: an inputshaft rotatably coupled to the actuator, a cycloidal disc rotatablycoupled to the input shaft, an output disc rotatably coupled to thecycloidal disc, and an output shaft extending from a first surface ofthe output disc, wherein rotation of the output shaft cause a change inthe relative distance between the first end and the second end.
 2. Theadjustable implant of claim 1, wherein the input shaft is mounted to aneccentric bearing and the cycloidal disc is configured to rotate aboutthe eccentric bearing.
 3. The adjustable implant of claim 2, wherein thecycloidal disc comprises a central aperture configured to receive theeccentric bearing therein, and a plurality of holes circumferentiallyspaced about the central aperture.
 4. The adjustable implant of claim 3,wherein the output disc comprises a plurality of pins extending from asecond surface of the output disc opposite the first surface, whereinthe plurality of pins are configured to engage the plurality of holes inthe cycloidal disc.
 5. The adjustable implant of claim 1, wherein thecycloidal disc comprises a plurality of lobes circumferentially spacedabout a perimeter of the cycloidal disc.
 6. The adjustable implant ofclaim 5, further comprising a plurality of circumferentially orientedring pins configured to engage the plurality of lobes.
 7. The implant ofclaim 1, wherein the actuator comprises a rotatable permanent magnetconfigured to be rotated by a rotating magnetic field.
 8. The implant ofclaim 7, wherein the rotatable permanent magnet is disposed within aninternal cavity of a magnet housing rotatably coupled to the inputshaft.
 9. The implant of claim 1, wherein the actuator comprises a motorcoupled to a power source.
 10. The adjustable implant of claim 1,wherein the cycloidal drive comprises one gear stage and has a speedreduction ratio of up to about 119:1.
 11. The adjustable implant ofclaim 1, wherein the cycloidal drive comprises two gear stages and has aspeed reduction ratio of up to about 7569:1.
 12. A system comprising:the adjustable implant of claim 1; and an external adjustment deviceconfigured to activate the actuator.
 13. The system of claim 12, whereinthe cycloidal disc of the adjustable implant comprises a plurality oflobes circumferentially spaced about a perimeter of the cycloidal disc.14. The system of claim 13, further comprising a plurality ofcircumferentially oriented ring pins configured to engage the pluralityof lobes.
 15. A method comprising: transcutaneously actuating anactuator of an adjustable implant implanted in a subject, wherein theactuating causes: an input shaft coupled to the actuator to rotate; acycloidal disc coupled to the input shaft to rotate; an output disccoupled to the cycloidal disc to rotate; an output shaft coupled to theoutput disc to rotate; and a distance between a first end and a secondend of the adjustable implant to change.
 16. The method of claim 15,further comprising: affixing a first end of the adjustable implant to afirst location of the subject; and affixing a second end of theadjustable implant to a second location of the subject.
 17. The methodof claim 15, wherein transcutaneously actuating the actuator includesgenerating a rotating magnetic field that rotates a permanent magnet ofthe actuator.
 18. The method of claim 15, wherein the rotation of thecycloidal disc is about an eccentric bearing to which the input shaft ismounted.
 19. The method of claim 15, wherein the cycloidal disccomprises a central aperture configured to receive the eccentric bearingtherein, and a plurality of holes circumferentially spaced about thecentral aperture.
 20. The method of claim 15, wherein the output disccomprises a plurality of pins extending from a second surface of theoutput disc opposite the first surface, wherein the plurality of pinsengage the plurality of holes in the cycloidal disc.